Semi-persistent scheduled resource release procedure in a mobile communication network

ABSTRACT

A semi-persistent resource scheduling (SPS) allocation of a user equipment is deactivated in an LTE-based mobile communication system without requiring changes to the Physical layer-to-MAC layer interface and/or changes to PDCCH formats agreed by the 3GPP. A combination of NDI value and MCS index is defined that commands release of SPS resources. An alternative solution proposed defines a special transport block size that when signaled in a PDCCH commands release of SPS resources.

This application is a continuation of U.S. patent application Ser. No.14/791,569, filed Jul. 6, 2015, which is a continuation of U.S. patentapplication Ser. No. 13/633,792, filed Oct. 2, 2012 (now U.S. Pat. No.9,094,965), which is a continuation of U.S. patent application Ser. No.13/062,674, filed May 13, 2011 (now U.S. Pat. No. 8,320,319), which isthe U.S. national phase of International Application No.PCT/EP2009/005831 filed Aug. 11, 2009, which designated the U.S. andclaims priority to EP 08016365.2 filed Sep. 17, 2008 and EP 08022171.6filed Dec. 19, 2008, the entire contents of each of which areincorporated herein by reference.

FIELD

The invention relates to a method for deactivating a semi-persistentresource allocation of a user equipment in an LTE-based mobilecommunication system. Furthermore, the invention also related to a userequipment and an eNode B implementing this method.

TECHNICAL BACKGROUND

Long Term Evolution (LTE)

Third-generation mobile systems (3G) based on WCDMA (Wideband CodeDivision Multiple Access) radio-access technology are being deployed ona broad scale all around the world. A first step in enhancing orevolving this technology entails introducing High-Speed Downlink PacketAccess (HSDPA) and an enhanced uplink, also referred to as High SpeedUplink Packet Access (HSUPA), giving a radio-access technology that ishighly competitive.

In a longer time perspective it is, however, necessary to be preparedfor further increasing user demands and an even tougher competition fromnew radio access technologies. To meet this challenge, 3GPP hasinitiated the study item Evolved UTRA and UTRAN (see 3GPP Tdoc.RP-040461, “Proposed Study Item on Evolved UTRA and UTRAN”, and 3GPP TR25.912: “Feasibility study for evolved Universal Terrestrial RadioAccess (UTRA) and Universal Terrestrial Radio Access Network (UTRAN)”,version 7.2.0, June 2007, available at http://www.3gpp.org and bothbeing incorporated herein by reference), aiming at studying means toachieve additional substantial leaps in terms of service provisioningand cost reduction. As a basis for this work, 3GPP has concluded on aset of targets and requirements for this long-term evolution (LTE) (see3GPP TR 25.913, “Requirements for Evolved UTRA and Evolved UTRAN”,version 7.3.0, March 2006, available at http://www.3gpp.org,incorporated herein by reference) including for example:

Peak data rates exceeding 100 Mbps for the downlink direction and 50Mbps for the uplink direction.

Mean user throughput improved by factors 2 and 3 for uplink and downlinkrespectively.

Cell-edge user throughput improved by a factor 2 for uplink anddownlink.

Uplink and downlink spectrum efficiency improved by factors 2 and 3respectively.

Significantly reduced control-plane latency.

Reduced cost for operator and end user.

Spectrum flexibility, enabling deployment in many different spectrumallocations.

The ability to provide high bit rates is a key measure for LTE. Multipleparallel data stream transmission to a single terminal, usingmultiple-input-multiple-output (MIMO) techniques, is one importantcomponent to reach this. Larger transmission bandwidth and at the sametime flexible spectrum allocation are other pieces to consider whendeciding what radio access technique to use. The choice of adaptivemulti-layer OFDM, AML-OFDM, in downlink will not only facilitate tooperate at different bandwidths in general but also large bandwidths forhigh data rates in particular. Varying spectrum allocations, rangingfrom 1.25 MHz to 20 MHz, are supported by allocating correspondingnumbers of AML-OFDM subcarriers. Operation in both paired and unpairedspectrum is possible as both time-division and frequency-division duplexis supported by AML-OFDM.

LTE Architecture

The overall architecture is shown in FIG. 1 and a more detailedrepresentation of the E-UTRAN architecture is given in FIG. 2. TheE-UTRAN consists of base stations (referred to as Node Bs or eNode Bs inthe 3GPP terminology), providing the E-UTRA user plane(PDCP/RLC/MAC/PHY) and control plane (Radio Resource Control—RRC)protocol terminations towards the mobile terminal (referred to as UE inthe 3GPP terminology).

The eNode B hosts the Physical (PHY), Medium Access Control (MAC), RadioLink Control (RLC), and Packet Data Control Protocol (PDCP) layers thatinclude the functionality of user-plane header-compression andencryption. It also offers Radio Resource Control (RRC) functionalitycorresponding to the control plane. It performs many functions includingradio resource management, admission control, scheduling, enforcement ofnegotiated UL QoS, cell information broadcast, ciphering/deciphering ofuser and control plane data, and compression/decompression of DL/UL userplane packet headers.

The eNode Bs are interconnected with each other by means of the X2interface. The eNode Bs are also connected by means of the S1 interfaceto the EPC (Evolved Packet Core), more specifically to the MME (MobilityManagement Entity) by means of the S1-MME and to the Serving Gateway(SGW) by means of the S1-U. The S1 interface supports a many-to-manyrelation between MMEs/Serving Gateways and eNode Bs. The SGW routes andforwards user data packets, while also acting as the mobility anchor forthe user plane during inter-eNode B handovers and as the anchor formobility between LTE and other 3GPP technologies (terminating S4interface and relaying the traffic between 2G/3G systems and PDN GW).For idle state UEs, the SGW terminates the downlink data path andtriggers paging when downlink data arrives for the UE. It manages andstores UE contexts, e.g., parameters of the IP bearer service, networkinternal routing information. It also performs replication of the usertraffic in case of lawful interception.

The MME is the key control-node for the LTE access-network. It isresponsible for idle mode UE tracking and paging procedure includingretransmissions. It is involved in the bearer activation/deactivationprocess and is also responsible for choosing the SGW for a UE at theinitial attach and at time of intra-LTE handover involving Core Network(CN) node relocation. It is responsible for authenticating the user (byinteracting with the HSS).

The Non-Access Stratum (NAS) signaling terminates at the MME and it isalso responsible for generation and allocation of temporary identitiesto UEs. It checks the authorization of the UE to camp on the serviceprovider's Public Land Mobile Network (PLMN) and enforces UE roamingrestrictions. The MME is the termination point in the network forciphering/integrity protection for NAS signaling and handles thesecurity key management. Lawful interception of signaling is alsosupported by the MME. The MME also provides the control plane functionfor mobility between LTE and 2G/3G access networks with the S3 interfaceterminating at the MME from the SGSN. The MME also terminates the S6ainterface towards the home HSS for roaming UEs.

OFDM with Frequency-Domain Adaptation

The AML-OFDM-based (AML-OFDM=Adaptive MultiLayer-Orthogonal FrequencyDivision Multiplex) downlink has a frequency structure based on a largenumber of individual sub-carriers with a spacing of 15 kHz. Thisfrequency granularity facilitates to implement dual-mode UTRA/E-UTRAterminals. The ability to reach high bit rates is highly dependent onshort delays in the system and a prerequisite for this is shortsub-frame duration. Consequently, the LTE sub-frame duration is set asshort as 1 ms in order to minimize the radio-interface latency. In orderto handle different delay spreads and corresponding cell sizes with amodest overhead the OFDM cyclic prefix length can assume two differentvalues. The shorter 4.7 ms cyclic prefix is enough to handle the delayspread for most unicast scenarios. With the longer cyclic prefix of 16.7ms very large cells, up to and exceeding 120 km cell radius, with largeamounts of time dispersion can be handled. In this case the length isextended by reducing the number of OFDM symbols in a sub-frame.

The basic principle of Orthogonal Frequency Division Multiplexing (OFDM)is to split the frequency band into a number of narrowband channels.Therefore, OFDM allows transmitting data on relatively flat parallelchannels (subcarriers) even if the channel of the whole frequency bandis frequency selective due to a multipath environment. Since thesubcarriers experience different channel states, the capacities of thesubcarriers vary and permit a transmission on each subcarrier with adistinct data-rate. Hence, subcarrier-wise (frequency domain) LinkAdaptation (LA) by means of Adaptive Modulation and Coding (AMC)increases the radio efficiency by transmitting different data-rates overthe subcarriers. OFDMA allows multiple users to transmit simultaneouslyon the different subcarriers per OFDM symbol. Since the probability thatall users experience a deep fade in a particular subcarrier is very low,it can be assured that subcarriers are assigned to the users who seegood channel gains on the corresponding sub-carriers. When allocatingresources in the downlink to different users in a cell, the schedulertakes information on the channel status experienced by the users for thesubcarriers into account. The control information signaled by the users,i.e., CQI, allows the scheduler to exploit the multi-user diversity,thereby increasing the spectral efficiency.

Localized vs. Distributed Mode

Two different resource allocation methods can be distinguished upon whenconsidering a radio access scheme that distribute available frequencyspectrum among different users as in OFDMA. The first allocation mode or“localized mode” tries to benefit fully from frequency scheduling gainby allocating the subcarriers on which a specific UE experiences thebest radio channel conditions. Since this scheduling mode requiresassociated signaling (resource allocation signaling, CQI in uplink),this mode would be best suited for non-real time, high data rateoriented services. In the localized resource allocation mode a user isallocated continuous blocks of subcarriers.

The second resource allocation mode or “distributed mode” relies on thefrequency diversity effect to achieve transmission robustness byallocating resources that are scattered over time and frequency grid.The fundamental difference with localized mode is that the resourceallocation algorithm does not try to allocate the physical resourcesbased on some knowledge on the reception quality at the receiver butselect more or less randomly the resource it allocates to a particularUE. This distributed resource allocation method seems to be best suitedfor real-time services as less associated signaling (no fast CQI, nofast allocation signaling) relative to “localized mode” is required.

The two different resource allocation methods are shown in FIG. 3 andFIG. 4 for an OFDMA based radio access scheme. As can be seen from FIG.3, which depicts the localized transmission mode, the localized mode ischaracterized by the transmitted signal having a continuous spectrumthat occupies a part of the total available spectrum. Different symbolrates (corresponding to different data rates) of the transmitted signalimply different bandwidths (time/frequency bins) of a localized signal.On the other hand, as can be seen from FIG. 4, the distributed mode ischaracterized by the transmitted signal having a non-continuous spectrumthat is distributed over more or less the entire system bandwidth(time/frequency bins).

Hybrid ARQ Schemes

A common technique for error detection and correction in packettransmission systems over unreliable channels is called hybrid AutomaticRepeat request (HARM). Hybrid ARQ is a combination of Forward ErrorCorrection (FEC) and ARQ.

If a FEC encoded packet is transmitted and the receiver fails to decodethe packet correctly (errors are usually checked by a CRC (CyclicRedundancy Check)), the receiver requests a retransmission of thepacket. Generally (and throughout this document) the transmission ofadditional information is called “retransmission (of a packet)”,although this retransmission does not necessarily mean a transmission ofthe same encoded information, but could also mean the transmission ofany information belonging to the packet (e.g., additional redundancyinformation).

Depending on the information (generally code-bits/symbols), of which thetransmission is composed, and depending on how the receiver processesthe information, the following Hybrid ARQ schemes are defined:

In Type I HARQ schemes, the information of the encoded packet isdiscarded and a retransmission is requested, if the receiver fails todecode a packet correctly. This implies that all transmissions aredecoded separately. Generally, retransmissions contain identicalinformation (code-bits/symbols) to the initial transmission.

In Type II HARQ schemes, a retransmission is requested, if the receiverfails to decode a packet correctly, where the receiver stores theinformation of the (erroneous received) encoded packet as softinformation (soft-bits/symbols). This implies that a soft-buffer isrequired at the receiver. Retransmissions can be composed out ofidentical, partly identical or non-identical information(code-bits/symbols) according to the same packet as earliertransmissions. When receiving a retransmission the receiver combines thestored information from the soft-buffer and the currently receivedinformation and tries to decode the packet based on the combinedinformation. (The receiver can also try to decode the transmissionindividually, however generally performance increases when combiningtransmissions.) The combining of transmissions refers to so-calledsoft-combining, where multiple received code-bits/symbols are likelihoodcombined and solely received code-bits/symbols are code combined. Commonmethods for soft-combining are Maximum Ratio Combining (MRC) of receivedmodulation symbols and log-likelihood-ratio (LLR) combining (LLRcombining only works for code-bits).

Type II schemes are more sophisticated than Type I schemes, since theprobability for correct reception of a packet increases with receiveretransmissions. This increase comes at the cost of a required hybridARQ soft-buffer at the receiver. This scheme can be used to performdynamic link adaptation by controlling the amount of information to beretransmitted. E.g., if the receiver detects that decoding has been“almost” successful, it can request only a small piece of informationfor the next retransmission (smaller number of code-bits/symbols than inprevious transmission) to be transmitted. In this case it might happenthat it is even theoretically not possible to decode the packetcorrectly by only considering this retransmission by itself(non-self-decodable retransmissions).

Type III HARQ schemes may be considered a subset of Type II schemes: Inaddition to the requirements of a Type II scheme each transmission in aType III scheme must be self-decodable.

HARQ Protocol Operation for Unicast Data Transmissions

A common technique for error detection and correction in packettransmission systems over unreliable channels is called hybrid AutomaticRepeat request (HARQ). Hybrid ARQ is a combination of Forward ErrorCorrection (FEC) and ARQ.

If a FEC encoded packet is transmitted and the receiver fails to decodethe packet correctly (errors are usually checked by a CRC (CyclicRedundancy Check)), the receiver requests a retransmission of thepacket.

In LTE there are two levels of retransmissions for providingreliability, namely, HARQ at the MAC layer and outer ARQ at the RLClayer. The outer ARQ is required to handle residual errors that are notcorrected by HARQ that is kept simple by the use of a single biterror-feedback mechanism, i.e., ACK/NACK. An N-process stop-and-waitHARQ is employed that has asynchronous retransmissions in the downlinkand synchronous retransmissions in the uplink.

Synchronous HARQ means that the retransmissions of HARQ blocks occur atpre-defined periodic intervals. Hence, no explicit signaling is requiredto indicate to the receiver the retransmission schedule.

Asynchronous HARQ offers the flexibility of scheduling retransmissionsbased on air interface conditions. In this case some identification ofthe HARQ process needs to be signaled in order to allow for a correctcombining and protocol operation. In 3GPP LTE systems, HARQ operationswith eight processes is used. The HARQ protocol operation for downlinkdata transmission will be similar or even identical to HSDPA.

In uplink HARQ protocol operation there are two different options on howto schedule a retransmission. Retransmissions are either “scheduled” bya NACK (also referred to as a synchronous non-adaptive retransmission)or are explicitly scheduled by the network by transmitting a PDCCH (alsoreferred to as synchronous adaptive retransmissions). In case of asynchronous non-adaptive retransmission the retransmission will use thesame parameters as the previous uplink transmission, i.e., theretransmission will be signaled on the same physical channel resources,respectively uses the same modulation scheme/transport format.

Since synchronous adaptive retransmission are explicitly scheduled viaPDCCH, the eNode B has the possibility to change certain parameters forthe retransmission. A retransmission could be for example scheduled on adifferent frequency resource in order to avoid fragmentation in theuplink, or eNode B could change the modulation scheme or alternativelyindicate to the user equipment what redundancy version to use for theretransmission. It should be noted that the HARQ feedback (ACK/NACK) andPDCCH signaling occurs at the same timing. Therefore the user equipmentonly needs to check once whether a synchronous non-adaptiveretransmission is triggered (i.e., only a NACK is received) or whethereNode B requests a synchronous adaptive retransmission (i.e., PDCCH issignaled).

L1/L2 Control Signaling

In order to inform the scheduled users about their allocation status,transport format and other data related information (e.g., HARQ) L1/L2control signaling is transmitted on the downlink along with the data.This control signaling is multiplexed with the downlink data in asub-frame (assuming that the user allocation can change from sub-frameto sub-frame). Here, it should be noted, that user allocation might alsobe performed on a TTI (Transmission Time Interval) basis, where the TTIlength is a multiple of the sub-frames. The TTI length may be fixed in aservice area for all users, may be different for different users, or mayeven be dynamic for each user. Generally, then the L1/2 controlsignaling needs only be transmitted once per TTI.

The L1/L2 control signaling is transmitted on the Physical DownlinkControl Channel (PDCCH). It should be noted that assignments for uplinkdata transmissions, uplink (scheduling) grants, are also transmitted onthe PDCCH.

Generally, the information sent on the L1/L2 control signaling may beseparated into the two categories, Shared Control Information andDedicated Control information:

Shared Control Information (SCI) Carrying Cat 1 Information

The SCI part of the L1/L2 control signaling contains information relatedto the resource allocation (indication). The SCI typically contains thefollowing information:

User identity, indicating the user which is allocated.

RB allocation information, indicating the resources (Resource Blocks,RBs) on which a user is allocated. Note, that the number of RBs on whicha user is allocated can be dynamic.

Duration of assignment (optional), if an assignment over multiplesub-frames (or TTIs) is possible.

Depending on the setup of other channels and the setup of the DedicatedControl Information (DCI), the SCI may additionally contain informationsuch as ACK/NACK for uplink transmission, uplink scheduling information,information on the DCI (resource, MCS, etc.).

Dedicated Control Information (DCI) Carrying Cat 2/3 Information

The DCI part of the L1/L2 control signaling contains information relatedto the transmission format (Cat 2) of the data transmitted to ascheduled user indicated by Cat 1. Moreover, in case of application of(hybrid) ARQ it carries HARQ (Cat 3) information. The DCI needs only tobe decoded by the user scheduled according to Cat 1.

The DCI typically contains information on:

Cat 2: Modulation scheme, transport-block (payload) size (or codingrate), MIMO related information, etc. (Note, either the transport-block(or payload size) or the code rate can be signaled. In any case theseparameters can be calculated from each other by using the modulationscheme information and the resource information (number of allocatedRBs)).

Cat 3: HARQ related information, e.g., hybrid ARQ process number,redundancy version, retransmission sequence number.

Details on L1/L2 Control Signaling Information

For downlink data transmissions L1/L2 control signaling is transmittedon a separate physical channel (PDCCH). This L1/L2 control signalingtypically contains information on:

The physical resource(s) on which the data is transmitted (e.g.,subcarriers or subcarrier blocks in case of OFDM, codes in case ofCDMA). This information allows the UE (receiver) to identify theresources on which the data is transmitted.

The transport format, which is used for the transmission. This can bethe transport block size of the data (payload size, information bitssize), the MCS (Modulation and Coding Scheme) level, the SpectralEfficiency, the code rate, etc. This information (usually together withthe resource allocation) allows the user equipment (receiver) toidentify the information bit size, the modulation scheme and the coderate in order to start the demodulation, the de-rate-matching and thedecoding process. In some cases the modulation scheme may be signaledexplicitly.

Hybrid ARQ (HARQ) information:

Process number: Allows the user equipment to identify the Hybrid ARQprocess on which the data is mapped.

Sequence number or new data indicator: Allows the user equipment toidentify if the transmission is a new packet or a retransmitted packet.

Redundancy and/or constellation version: Tells the user equipment, whichhybrid ARQ redundancy version is used (required for de-rate-matching)and/or which modulation constellation version is used (required fordemodulation).

UE Identity (UE ID): Tells for which user equipment the L1/L2 controlsignaling is intended for. In typical implementations this informationis used to mask the CRC of the L1/L2 control signaling in order toprevent other user equipments to read this information.

To enable an uplink packet data transmission, L1/L2 control signaling istransmitted on the downlink (PDCCH) to tell the user equipment about thetransmission details. This L1/L2 control signaling typically containsinformation on:

The physical resource(s) on which the user equipment should transmit thedata (e.g., subcarriers or subcarrier blocks in case of OFDM, codes incase of CDMA).

The transport Format, the UE should use for the transmission. This canbe the transport block size of the data (payload size, information bitssize), the MCS (Modulation and Coding Scheme) level, the SpectralEfficiency, the code rate, etc. This information (usually together withthe resource allocation) allows the user equipment (transmitter) to pickthe information bit size, the modulation scheme and the code rate inorder to start the modulation, the rate-matching and the encodingprocess. In some cases the modulation scheme maybe signaled explicitly.

Hybrid ARQ Information:

Process number: Tells the user equipment from which Hybrid ARQ processit should pick the data.

Sequence number or new data indicator: Tells the user equipment totransmit a new packet or to retransmit a packet.

Redundancy and/or constellation version: Tells the user equipment, whichhybrid ARQ redundancy version to use (required for rate-matching) and/orwhich modulation constellation version to use (required for modulation).

UE Identity (UE ID): Tells which user equipment should transmit data. Intypical implementations this information is used to mask the CRC of theL1/L2 control signaling in order to prevent other user equipments toread this information.

There are several different flavors how to exactly transmit theinformation pieces mentioned above. Moreover, the L1/L2 controlinformation may also contain additional information or may omit some ofthe information. E.g.:

HARQ process number may not be needed in case of a synchronous HARQprotocol.

A redundancy and/or constellation version may not be needed if ChaseCombining is used (always the same redundancy and/or constellationversion) or if the sequence of redundancy and/or constellation versionsis predefined.

Power control information may be additionally included in the controlsignaling.

MIMO related control information, such as, e.g., precoding, may beadditionally included in the control signaling.

In case of multi-codeword MIMO transmission transport format and/or HARQinformation for multiple code words may be included.

For uplink resource assignments (for the Physical Uplink SharedChannel—PUSCH) signaled on the PDCCH in LTE, the L1/L2 controlinformation does not contain a HARQ process number, since a synchronousHARQ protocol is employed for LTE uplink. The HARQ process to be usedfor an uplink transmission is given by the timing. Furthermore it shouldbe noted that the redundancy version (RV) information is jointly encodedwith the transport format information, i.e., the redundancy versioninformation is embedded in the transport format (TF) field. The TF fieldrespectively MCS field (Modulation and Coding Scheme field) has forexample a size of 5 bits, which corresponds to 32 indices. Three TF/MCStable indices are reserved for indicating RVs 1, 2 or 3. The remainingMCS table indices are used to signal the MCS level (transport blocksize—TBS) implicitly indicating RV0. The TBS/RV signaling for uplinkassignments on PDCCH is shown in Table 1 below. An exemplary PDCCH foruplink resource assignments is shown in FIG. 5. The fields FH (FrequencyHopping), Cyclic shift and CQI (Channel Quality Index) are physicallayer parameters and of no specific importance for understanding theinvention described herein, so that their description is omitted. Thesize of the CRC field of the PDCCH is 16 bits. For further, moredetailed information on the information fields contained in a PDCCH foruplink resource assignments, e.g., DCI format 0, it is referred tosection 5.3.3.1 of 3GPP TS 36.212 “Evolved Universal Terrestrial RadioAccess (E-UTRA); Multiplexing and channel coding (Release 8)”, version8.3.0, June 2008, available at http://www.3gpp.org and the entiredocument being incorporated herein by reference. Even though the fieldproviding transport format respectively modulation and coding scheme andredundancy version information is referred to as “modulation and codingscheme and redundancy version” it will be for the further description ofthe invention only referred to as modulation and coding scheme (MCS)field.

For downlink resource assignments (for the Physical Downlink SharedChannel—PDSCH) signaled on PDCCH in LTE the redundancy version issignaled separately in a two-bit field. Furthermore the modulation orderinformation is jointly encoded with the transport format information,similar to the uplink case there is 5 bit MCS field signaled on PDCCH.Three of the indices are reserved for the signaling of an explicitmodulation order, i.e., those indices do not provide any transportformat (transport block size) information. The remaining 29 indicessignal modulation order and transport block size information as shown inTable 3 below. For further, more detailed information on the PDCCHformats for downlink resource assignment it is again referred to section5.3.3.1 of 3GPP TS 36.212. For example, section 5.3.3.1.3 describes theDCI format 1A, which is one of the DCI formats for scheduling PDSCH. Fordownlink assignments the field providing transport block size andmodulation order information is referred to as “modulation and codingscheme” field the term that will also be used in the description of thisinvention.

UL/DL Grant Reception Behavior

Generally the grant reception procedure (i.e., the procedure ofreceiving a resource assignment) is split between Physical layer and MAClayer. The Physical layer detects an uplink/downlink resource assignmenton the PDCCH, extracts and determines certain information from the PDCCHfields and reports this to MAC layer. The MAC layer is responsible forthe protocol procedures, i.e., HARQ protocol operation foruplink/downlink transmissions. Also the scheduling procedures fordynamic as well as semi-persistent scheduling are handled within the MAClayer.

When receiving a resource assignment on the PDCCH for uplinkrespectively downlink, the physical layer needs to determine certaininformation from received PDCCH fields which are required for thefurther processing of the assignments in MAC layer. As described in 3GPPTS 36.213, the Physical layer needs to determine the modulation orderand transport block size in the PDSCH for a downlink resourceassignment. The calculation of modulation order and transport block sizeis described in section 7.1.7 of 3GPP TS 36.213. Transport block sizetogether with the HARQ process ID and the NDI bit is delivered to theMAC layer, which requires this information for performing the downlinkHARQ protocol operation. The information delivered from Physical layer(Layer 1) to MAC (Layer 2) is also referred to as HARQ information.

Similar to the downlink, the Physical layer calculates modulation orderand transport block size from received PDCCH containing the uplinkresource assignment as described in section 8.6 of 3GPP TS 36.213. ThePhysical layer reports the calculated transport block size, redundancyversion (RV) as well as NDI information of the PDCCH within the HARQinformation to the MAC layer.

Semi-Persistent Scheduling (SPS)

In the downlink and uplink, the scheduling eNode B dynamically allocatesresources to user equipments at each transmission time interval via theL1/L2 control channel(s) (PDCCH) where the user equipments are addressedvia their specific C-RNTIs. As already mentioned before the CRC of aPDCCH is masked with the addressed user equipment's C-RNTI (so-calleddynamic PDCCH). Only a user equipment with a matching C-RNTI can decodethe PDCCH content correctly, i.e., the CRC check is positive. This kindof PDCCH signaling is also referred to as dynamic (scheduling) grant. Auser equipment monitors at each transmission time interval the L1/L2control channel(s) for a dynamic grant in order to find a possibleallocation (downlink and uplink) it is assigned to.

In addition, E-UTRAN can allocate uplink/downlink resources for initialHARQ transmissions persistently. When required, retransmissions areexplicitly signaled via the L1/L2 control channel(s). Sinceretransmissions are scheduled, this kind of operation is referred to assemi-persistent scheduling (SPS), i.e., resources are allocated to theuser equipment on a semi-persistent basis (semi-persistent resourceallocation). The benefit is that PDCCH resources for initial HARQtransmissions are saved. For details on semi-persistent scheduling, see3GPP TS 36.300, “Evolved Universal Terrestrial Radio Access (E-UTRA) andEvolved Universal Terrestrial Radio Access Network (E-UTRAN); Overalldescription; Stage 2 (Release 8)”, version 8.5.0, June 2008 or 3GPP TS36.321 “Evolved Universal Terrestrial Radio Access (E-UTRA); MediumAccess Control (MAC) protocol specification (Release 8)”, version 8.2.0,June 2008, both available at http://www.3gpp.org and incorporated hereinby reference.

One example for a service, which might be scheduled usingsemi-persistent scheduling is Voice over IP (VoiP). Every 20 ms a VoIPpacket is generated at the codec during a talk-spurt. Therefore eNode Bcould allocated uplink or respectively downlink resource persistentlyevery 20 ms, which could be then used for the transmission of Voice overIP packets. In general, semi-persistent scheduling is beneficial forservices with a predictable traffic behavior, i.e., constant bit rate,packet arrival time is periodic.

The user equipment also monitors the PDCCHs in a sub-frame where it hasbeen allocated resources for an initial transmission persistently. Adynamic (scheduling) grant, i.e., PDCCH with a C-RNTI-masked CRC, canoverride a semi-persistent resource allocation. In case the userequipment finds its C-RNTI on the L1/L2 control channel(s) in thesub-frames where the sub-frame has a semi-persistent resource assigned,this L1/L2 control channel allocation overrides the semi-persistentresource allocation for that transmission time interval and the userequipment does follow the dynamic grant. When sub-frame does not find adynamic grant it will transmit/receive according to the semi-persistentresource allocation.

The configuration of semi-persistent scheduling is done by RRCsignaling. For example the periodicity, i.e., PS_PERIOD, of thepersistent allocation is signaled within Radio resource Control (RRC)signaling. The activation of a persistent allocation and also the exacttiming as well as the physical resources and transport format parametersare sent via PDCCH signaling. Once semi-persistent scheduling isactivated, the user equipment follows the semi-persistent resourceallocation according to the activation SPS PDCCH every PS_PERIOD.Essentially the user equipment stores the SPS activation PDCCH contentand follows the PDCCH with the signaled periodicity.

In order to distinguish a dynamic PDCCH from a PDCCH, which activatessemi-persistent scheduling, i.e., also referred to as SPS activationPDCCH, a separate identity is introduced. Basically, the CRC of a SPSactivation PDCCH is masked with this additional identity which is in thefollowing referred to as SPS C-RNTI. The size of the SPS C-RNTI is also16 bits, same as the normal C-RNTI. Furthermore the SPS C-RNTI is alsouser equipment-specific, i.e., each user equipment configured forsemi-persistent scheduling is allocated a unique SPS C-RNTI.

In case a user equipment detects a semi-persistent resource allocationis activated by a corresponding SPS PDCCH, the user equipment will storethe PDCCH content (i.e., the semi-persistent resource assignment) andapply it every semi-persistent scheduling interval, i.e., periodicitysignaled via RRC. As already mentioned, a dynamic allocation, i.e.,signaled on dynamic PDCCH, is only a “one-time allocation”.

Similar to the activation of semi-persistent scheduling, the eNode Balso can deactivate semi-persistent scheduling. There are severaloptions how a semi-persistent scheduling de-allocation can be signaled.One option would be to use PDCCH signaling, i.e., SPS PDCCH indicating azero size resource allocation, another option would be to use MACcontrol signaling.

Reduction of SPS False Activation

When the user equipment monitors the PDCCH for assignments, there isalways a certain probability (false alarm rate), that the user equipmentfalsely considers a PDCCH destined to itself. Essentially, situationsmay occur where the CRC check of the PDCCH is correct even though thePDCCH was not intended for this user equipment, i.e., CRC passes eventhough there is a UE identifier (UE ID) mismatch (unintended user).These so-called “false alarms” might occur, if the two effects oftransmission errors caused by the radio channel and UE ID mismatchcancel each other. The probability of a falsely positive decoded PDCCHdepends on the CRC length. The longer the CRC length, the lower theprobability that a CRC-protected message is erroneously decodedcorrectly. With the CRC size of 16 bit the false alarm probability wouldbe 1.5e-05. It should be noted that due to the introduction of aseparate identity for the discrimination of dynamic PDCCHs (dynamicC-RNTI) and SPS PDCCHs (SPS C-RNTI), false alarms are even morefrequent.

On the first glance the probability might appear to be sufficiently low,however the impacts of a falsely positive decoded semi-persistentscheduling PDCCH are quite severe as will be outlined in the following.Since the effects are in particular for uplink persistent allocationcritical, the main focus lies on falsely activated uplinksemi-persistent resource allocations.

In case the UE falsely detects a SPS UL PDCCH (i.e., an uplink resourceassignment for a semi-persistent resource allocation), the content ofthe PDCCH is some random value. Consequently UE transmits on PUSCH usingsome random RB location and bandwidth found in the false positive grant,which subjects the eNode B to UL interferences. With 50% probability UEjams more than half the bandwidth of the system since the ResourceAllocation field is random. The user equipment is looking for ACK/NACKin the location corresponding to the (false positive) semi-persistentuplink resource allocation. The eNode B is not transmitting any data tothe user equipment and the user equipment will decode the“acknowledgment” for its transmission (ACK/NACK) pretty random. When aNACK is received user equipment performs a synchronous non-adaptiveretransmission. When ACK is received user equipment is suspended untilthe next SPS occasion, and the MAC may assume the transport block hasbeen successfully received and decoded at the eNode B.

Essentially as a consequence of a false activation of a semi-persistentresource allocation for the uplink, a talk spurt can be lost completelyor partially several times during a normal voice call. In addition, afalse activation of a semi-persistent resource allocation for the uplinkcauses unnecessary interference to the system.

Given the severe consequences it is desirable to significantly increasethe average time of false semi-persistent scheduling activations. Onemeans to lower the false alarm rate to an acceptable level is to use a“Virtual CRC” in order to expand the 16-bit CRC: The length of the CRCfield can be virtually extended by setting fixed and known values tosome of the PDCCH fields that are not useful for semi-persistentscheduling activation. The user equipment shall ignore the PDCCH forsemi-persistent resource activation if the values in these fields arenot correct. Since MIMO operation with semi-persistent scheduling doesnot seem to be that useful, the corresponding PDCCH fields could be usedin order to the increase the virtual CRC length. One further example isthe NDI field. As already mentioned the NDI bit should be set to 0 on aPDCCH for semi-persistent scheduling activation. The false alarm ratecould be further reduced by restricting the set of transport blocksizes, which are valid for a semi-persistent scheduling activation.

As mentioned above, a semi-persistent scheduling resource release issignaled by means of an PDCCH similar to an SPS activation. In order touse the resource for SPS efficiently, it is desirable that resources canbe re-allocated quickly, for example in VoIP by means of explicitrelease of a persistent allocation during silence periods in speech,followed by a re-activation when the silence periods end. Therefore itshould be noted that at a semi-persistent scheduling resource release anSPS RRC configuration, e.g., PS_PERIOD, remains in place until changedby RRC signaling. Therefore PDCCH is used for an efficient explicitrelease (de-activation) of semi-persistent scheduling.

One possibility would be sending a semi-persistent scheduling activationwith a zero-size resource allocation. A zero-size allocation wouldcorrespond to a resource allocation of 0 physical resource blocks (RB)which would effectively deactivate the semi-persistent resourceallocation. This solution requires that a PDCCH message, i.e.,uplink/downlink resource assignment, is able to indicate “0RBs” as onepossible resource block allocation. Since this is not possible with thePDCCH formats agreed on in the 3GPP, a new “ORB” entry would need to beintroduced in resource block assignment field for PDSCH and PUSCH. Thiswould however also have impact on the Physical layer-to-MAC Layerinteraction in the user equipments, as the Physical layer would furtherneed to be adapted to inform the MAC layer on the deactivation of thesemi-persistent resource allocation.

SUMMARY

One object of the invention is to provide a mechanism for deactivating asemi-persistent resource allocation in a LTE system that is notrequiring any changes to the Physical layer-to-MAC layer interfaceand/or preferably no changes to the PDCCH formats agreed by the 3GPP.

The object is solved by the subject matter of the independent claims.Advantageous embodiments of the invention are subject matters of thedependent claims.

One aspect of the invention is to use (existing) physical controlchannel signaling related to a semi-persistent resource allocation fordeactivating the semi-persistent resource allocation to a user equipment(or in other words releasing the grant for the semi-persistent resourceallocation) by defining a special control channel signaling content as adeactivation command for the semi-persistent resource allocation. Morespecifically, the control channel signaling contains a New DataIndicator (NDI) and a modulation and coding scheme field, and a specificcombination of the New Data Indicator value and a modulation and codingscheme index signalled within the modulation and coding scheme field isdefined to indicate the deactivation of the semi-persistent resourceallocation.

According to a second alternative aspect of the invention, thesemi-persistent resource allocation is configured by RRC signaling. TheRRC signaling is indicating a special transport block size to the userequipment that, when indicated in a resource assignment for thesemi-persistent resource allocation on a physical control channel, iscommanding the user equipment to deactivate the semi-persistent resourceallocation.

Both aspects of the invention do not impact the user equipmentsoperation concerning the handling of resource assignments (grants) anddo therefore also not impact the interface between Physical layer andMAC layer as presently defined by the 3GPP.

The invention according to one embodiment is related to a method fordeactivating a semi-persistent resource allocation in an LTE-basedmobile communication system. The user equipment (a mobile terminal inthe 3GPP terminology) is receiving control signalling that is includinga New Data Indicator and a modulation and coding scheme field. Thecontrol signalling is received via a control channel (such as the PDCCH)from an eNode B (a base station in an LTE system). If the New DataIndicator and the modulation and coding scheme field of the controlsignalling indicate a predetermined combination of a New Data Indicatorvalue and a modulation and coding scheme index, the user equipment isdeactivating the semi-persistent resource allocation.

Another embodiment of the invention is directed to the operation of theeNode B. The eNode B generates for the user equipment control signallingcomprising a New Data Indicator and a modulation and coding schemefield. The New Data Indicator and the modulation and coding scheme fieldinclude a predetermined combination of a New Data Indicator value and amodulation and coding scheme index that is to cause the user equipmentto deactivate the semi-persistent resource allocation. The eNode Btransmits the control signalling via a control channel to the userequipment to thereby cause the user equipment to deactivate thesemi-persistent resource allocation.

According to a further embodiment of the invention, the predeterminedcombination of the New Data Indicator value and the modulation andcoding scheme index is the New Data Indicator value being 0 (indicatingan activation of semi-persistent scheduling) and the modulation andcoding scheme index indicating no transport block size Information.Hence, in this exemplary embodiment of the invention, indices of themodulation and coding scheme field are reused that are commonly not usedfor a resource assignment to activate or reactivate the semi-persistentresource allocation.

In an alternative embodiment of the invention, the predeterminedcombination of the New Data Indicator value and the modulation andcoding scheme index is the New Data Indicator value being 1 (indicatinga retransmission of a data packet) and the modulation and coding schemeindex indicating a transport block size to the user equipment that isdifferent from the transport block size of the initial transmission ofthe data. In this exemplary embodiment, the different transport blocksize for the retransmission is considered a release command for thegrant of the semi-persistent resource allocation so that thesemi-persistent resource allocation is deactivated.

In a further embodiment, the control signalling is protected by a CRCfield that is masked with an RNTI assigned to the user equipment foridentification in signalling procedures related to the semi-persistentresource allocation. This feature is not only protecting the content ofthe control signalling but also allows addressing the control signallingto the desired user equipment and its relation to semi-persistentscheduling, as described previously herein.

According to another embodiment of the invention, at least one field ofthe control signalling from the eNode B is set to a predetermined value,for validating said control signalling as a semi-persistent resourcedeactivation indication. This allows to lower the false alarm rate aswill be explained below in further detail.

In another embodiment, the concept of the invention is employed tohandle semi-persistent resource allocations for uplink and downlink. Themodulation and coding scheme field indicates one of plural modulationand coding scheme indices. Further it is assumed that there is a subsetof at least three indices that indicate no transport block sizeinformation. The user equipment is deactivating

a semi-persistent resource allocation for the uplink, in case a firstpredetermined modulation and coding scheme index of said subset isindicated in the modulation and coding scheme field,

a semi-persistent resource allocation for the downlink, in case a secondpredetermined modulation and coding scheme index of said subset isindicated in the modulation and coding scheme field, and

a semi-persistent resource allocation for the downlink and asemi-persistent resource allocation for the uplink, in case a thirdpredetermined modulation and coding scheme index of said subset isindicated in the modulation and coding scheme field.

In a different embodiment of the invention said control signalling isdownlink control signalling from the eNode B used for scheduling ofdownlink transmissions. Said control signalling includes the firstpredetermined modulation and coding scheme index for deactivating thesemi-persistent resource allocation for the uplink. By using thedownlink scheduling related control signalling for indicating the uplinksemi-persistent resource release, it is possible to reuse mechanismsapplied to only the downlink scheduling related control signalling foruplink purposes.

According to a further embodiment of the invention, the reception of thecontrol signalling is acknowledged by the user equipment by transmittingan ACK message to the eNode B. It is possible to acknowledge thereception of control signalling, whereas the prior art only foresees theacknowledgment of transport blocks. This increases the reliability ofthe semi-persistent resource release indication. Furthermore, theacknowledgment is applicable to the downlink scheduling related controlsignalling, thus allowing the acknowledgment for downlink schedulingrelated control signalling as well for the uplink indication ofsemi-persistent resource release.

The method according to another embodiment of the invention furthercomprises signalling from the eNode B to the user equipment an RRCmessage that indicates a periodicity of the semi-persistent resourceallocation and a range of allowable transport block sizes that can beconfigured by a control channel signalled from the eNode B to the userequipment. In a variation of this embodiment, the RRC message furtherindicates HARQ information on the HARQ process used for downlinktransmissions to the user equipment according to the semi-persistentresource allocation.

Another embodiment of the invention is related to an alternative methodfor deactivating a semi-persistent resource allocation of a userequipment in an LTE-based mobile communication system according to thesecond aspect of the invention. In this method the user equipmentreceives a RRC message configuring the semi-persistent resourceallocation and indicating a transport block size that when indicated incontrol signalling related to the semi-persistent resource allocation iscausing the user equipment to deactivate the semi-persistent resourceallocation. Moreover, the user equipment is receiving control signallingrelated to the semi-persistent resource allocation from an eNode B. Thecontrol signalling is yielding a transport block size for thesemi-persistent resource allocation. The user equipment deactivates thesemi-persistent resource allocation, if the transport block sizeindicated in the control signalling matches the transport block sizeindicated in the RRC message.

In a variation of this embodiment the control signalling is comprising aresource allocation field value that is indicating the number ofresource blocks allocated to the user equipment and a modulation andcoding scheme index that is indicating a modulation and coding scheme,the user equipment is further determining the transport block sizeyielded by the control signalling based on the resource allocation fieldvalue and the modulation and coding scheme index.

In another embodiment of the invention, the operation of an eNode B inaccordance with the above-mentioned alternative method for deactivatinga semi-persistent resource allocation of a user equipment in anLTE-based mobile communication system is considered. The eNode Btransmits a RRC message to the user equipment for configuring thesemi-persistent resource allocation. This RRC message is indicating atransport block size that when yielded by control signalling related tothe semi-persistent resource allocation is causing the user equipment todeactivate the semi-persistent resource allocation. Furthermore, theeNode B generates control signalling related to the semi-persistentresource allocation and yielding the transport block size indicated bysaid RRC message, and transmits the control signalling to the userequipment to thereby cause the user equipment to deactivate thesemi-persistent resource allocation.

In a further embodiment of the invention, the RRC message indicates theperiodicity of the semi-persistent resource allocation and a range ofallowable transport block sizes that can be used for the activation ofsemi-persistent scheduling. In a variation, the RRC message couldadditionally indicate HARQ information on the HARQ process used fordownlink transmissions according to the semi-persistent resourceallocation to the user equipment.

According to another embodiment of the invention, for uplinksemi-persistent scheduling, the modulation and coding scheme field isindicating one of plural predetermined indices. Thereby, a non-emptysubset of the predetermined indices is used to jointly encode modulationscheme, transport block size and redundancy version for an uplink datatransmission, while the remaining indices are used to encode only aredundancy version for an uplink data transmission.

Alternatively, for downlink semi-persistent scheduling, the modulationand coding scheme field is indicating one of plural predeterminedindices, wherein a non-empty subset of the predetermined indices is usedto jointly encode modulation scheme and transport block size for adownlink transmission to be received by the user equipment, while theremaining indices are used to encode only a modulation scheme for adownlink transmission.

In an exemplary embodiment of the invention, the control channel is aPDCCH and/or the control signalling is comprised of a resourceassignment to the user equipment.

Furthermore, the invention is also related to the apparatuses andcomputer readable media for performing the method for deactivating asemi-persistent resource allocation according to the various embodimentsand aspects of the invention described herein. In this connection,another embodiment of the invention is providing a user equipment foruse in an LTE-based mobile communication system that is comprising areceiver for receiving via a control channel from an eNode B controlsignalling that is including a New Data Indicator and a modulation andcoding scheme field, and a processing unit for deactivating thesemi-persistent resource allocation, if the New Data Indicator and themodulation and coding scheme field of the control signalling signal apredetermined combination of a New Data Indicator value and a modulationand coding scheme index.

The invention according to a further embodiment is related to an eNode Bfor use in an LTE-based mobile communication system that is comprising ascheduler for generating for the user equipment control signallingcomprising a New Data Indicator and a modulation and coding scheme fieldincluding a predetermined combination of a New Data Indicator value anda modulation and coding scheme index that is causing the user equipmentto deactivate the semi-persistent resource allocation, and a transmitterfor transmitting said control signalling via a control channel to theuser equipment to thereby cause the user equipment to deactivate thesemi-persistent resource allocation.

Likewise, the invention according to another embodiment is also relatedto a computer readable medium storing instructions that when executed bya processor of a user equipment cause the user equipment to deactivate asemi-persistent resource allocation in an LTE-based mobile communicationsystem, by receiving via a control channel from an eNode B controlsignalling that is including a New Data Indicator and a modulation andcoding scheme field, and deactivating the semi-persistent resourceallocation, if the New Data Indicator and the modulation and codingscheme field of the control signalling signal a predeterminedcombination of a New Data Indicator value and a modulation and codingscheme index.

Another embodiment of the invention is providing a computer readablemedium storing instructions that when executed by a processor of aneNode B, cause the eNode B to deactivate a semi-persistent resourceallocation of a user equipment by generating for the user equipmentcontrol signalling comprising a New Data Indicator and a modulation andcoding scheme field including a predetermined combination of a New DataIndicator value and a modulation and coding scheme index that is causingthe user equipment to deactivate the semi-persistent resourceallocation, and transmitting said control signalling via a controlchannel to the user equipment to thereby cause the user equipment todeactivate the semi-persistent resource allocation.

A further embodiment of the invention is related to the second aspect ofthe invention and a user equipment for use in an LTE-based mobilecommunication system, comprising a receiver for receiving a RRC messageconfiguring a semi-persistent resource allocation and indicating atransport block size that when indicated in control signalling relatedto the semi-persistent resource allocation is causing the user equipmentto deactivate the semi-persistent resource allocation. The receiver ofthe user equipment is adapted to receive control signalling related tothe semi-persistent resource allocation from an eNode B, wherein thecontrol signalling is yielding a transport block size for thesemi-persistent resource allocation. Furthermore, the user equipmentcomprises a processing unit for deactivating the semi-persistentresource allocation, if the transport block size indicated in thecontrol signalling matches the transport block size indicated in the RRCmessage.

In a variation, the control signalling is comprising a resourceallocation field value that is indicating the number of resource blocksallocated to the user equipment and a modulation and coding scheme indexthat is indicating a modulation and coding scheme, and the userequipment's processing unit is further adapted to determine saidtransport block size yielded by the control signalling based on theresource allocation field value and the modulation and coding schemeindex.

Another embodiment of the invention is related to an eNode B for use inan LTE-based mobile communication system, comprising a transmitter fortransmitting a RRC message to a user equipment for configuring asemi-persistent resource allocation, wherein the RRC message isindicating a transport block size that when yielded by controlsignalling related to the semi-persistent resource allocation is causingthe user equipment to deactivate the semi-persistent resourceallocation, a scheduler for generating control signalling related to thesemi-persistent resource allocation and yielding the transport blocksize indicated by said RRC message, and a transmitter for transmittingthe control signalling to the user equipment to thereby cause the userequipment to deactivate the semi-persistent resource allocation.

In a further embodiment, the invention is providing a computer readablemedium storing instructions that when executed by a processor of a userequipment cause the user equipment to deactivate a semi-persistentresource allocation in an LTE-based mobile communication system, byreceiving a RRC message configuring the semi-persistent resourceallocation and indicating a transport block size that when indicated incontrol signalling related to the semi-persistent resource allocation iscausing the user equipment to deactivate the semi-persistent resourceallocation, receiving control signalling related to the semi-persistentresource allocation from an eNode B, wherein the control signalling isyielding a transport block size for the semi-persistent resourceallocation, and deactivating the semi-persistent resource allocation, ifthe transport block size indicated in the control signalling matches thetransport block size indicated in the RRC message.

In a variation of this embodiment, the control signalling is comprisinga resource allocation field value that is indicating the number ofresource blocks allocated to the user equipment and a modulation andcoding scheme index that is indicating a modulation and coding scheme,and the computer readable medium is further storing instructions thatwhen executed by the processor of the user equipment cause same todetermine the transport block size yielded by the control signallingbased on the resource allocation field value and the modulation andcoding scheme index.

Another embodiment is related to a computer readable medium storinginstructions that when executed by a processor of an eNode B, cause theeNode B to deactivate a semi-persistent resource allocation of a userequipment by transmitting a RRC message to the user equipment forconfiguring the semi-persistent resource allocation, wherein the RRCmessage is indicating a transport block size that when yielded bycontrol signalling related to the semi-persistent resource allocation iscausing the user equipment to deactivate the semi-persistent resourceallocation, generating control signalling related to the semi-persistentresource allocation and yielding the transport block size indicated bysaid RRC message, and transmitting the control signalling to the userequipment to thereby cause the user equipment to deactivate thesemi-persistent resource allocation.

BRIEF DESCRIPTION OF THE FIGURES

In the following, the invention is described in more detail in referenceto the attached figures and drawings. Similar or corresponding detailsin the figures are marked with the same reference numerals.

FIG. 1 shows an exemplary high level architecture of a 3GPP LTE system,

FIG. 2 shows an exemplary overview of the E-UTRAN of the high levelarchitecture of a 3GPP LTE system in FIG. 1,

FIG. 3 shows an exemplary allocation of radio resources of an OFDMchannel in localized transmission mode,

FIG. 4 shows an exemplary allocation of radio resources of an OFDMchannel in distributed transmission mode,

FIG. 5 shows an exemplary format of a resource assignment message(PDCCH) for allocating uplink resources to a mobile terminal,

FIG. 6 shows an exemplary signaling procedure for activating an uplinksemi-persistent resource allocation between a user equipment (UE) and aneNode B according to an exemplary embodiment of the invention,

FIGS. 7 and 8 show different exemplary signaling procedure fordeactivating an uplink semi-persistent resource allocation between auser equipment (UE) and an eNode B according to exemplary embodiments ofthe invention,

FIGS. 9 and 10 show flow charts of the basic operation of the Physicallayer entity and the MAC-layer entity of a user equipment according toexemplary embodiments of the invention to realize a deactivation ofsemi-persistent scheduling,

FIG. 11 shows a flow chart of the basic operation of the Physical layerentity, the MAC-layer entity and the RRC entity in a user equipmentaccording to exemplary embodiments of the invention to realize adeactivation of semi-persistent scheduling, and

FIGS. 12 and 13 show exemplary RRC message formats for configuring asemi-persistent scheduling according to exemplary embodiments of theinvention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

The following paragraphs will describe various embodiments of theinvention. For exemplary purposes only, most of the embodiments areoutlined in relation to an (evolved) communication system according toLTE discussed in the Technical Background section above.

One aspect of the invention is to use (existing) physical controlchannel signaling related to a semi-persistent scheduling fordeactivating the semi-persistent resource allocation to a user equipment(or in other words releasing the grant for the semi-persistent resourceallocation) by defining a special combination of control channelsignaling values as a deactivation command for the semi-persistentresource allocation. More specifically, the physical control channelsignaling may be a resource assignment related to the semi-persistentresource allocation that is commonly used to allocate or reallocateradio resources to the user equipment for the semi-persistent resourceallocation. The control signaling, respectively the resource assignmentinformation is assumed to contain a New Data Indicator and a modulationand coding scheme field. A special combination of the New Data Indicatorvalue and a modulation and coding scheme index, which is signalledwithin the modulation and coding scheme field, is defined to indicatethe deactivation of the semi-persistent resource allocation (or in otherwords releases a previous resource assignment (grant) for thesemi-persistent resource allocation).

According to one embodiment of the invention, a semi-persistent resourceallocation in an LTE-based mobile communication system is deactivated bythe eNode B generating special control signalling information (e.g., aresource assignment) for the user equipment that is containing apredetermined combination of a New Data Indicator value and a modulationand coding scheme index that is to cause the user equipment todeactivate the semi-persistent resource allocation. The eNode B signalsthis control signalling information to the user equipment, which isreceiving the control signalling information and processes it. If theuser equipment detects the control signalling information to contain apredetermined combination of a New Data Indicator value and a modulationand coding scheme index, the user equipment is deactivating thesemi-persistent resource allocation.

There are different possibilities how to define the predeterminedcombination (or combinations) of a New Data Indicator value and amodulation and coding scheme index that are to release the grant for asemi-persistent resource allocation—which can be also referred to as aresource release command. In one example, the modulation and codingscheme index in the resource assignment is indicating no transport blocksize while the New Data Indicator is indicating an activation ofsemi-persistent scheduling i.e., is set to 0. As no initial datatransmission can be sent/received properly without having knowledge ofthe transport block size, a modulation and coding scheme indexindicating no transport block size is typically unused for a resourceassignment or reassignment in connection with semi-persistent schedulingand can therefore be used as a resource release command.

Another possibility to communicate a resource release command for asemi-persistent resource allocation is to indicate a change in thetransport block size for a retransmission of a semi-persistentlyscheduled data packet, which is especially applicable to scenarios whereHARQ in combination with soft-combining is used. In order to allow softcombining of different transmissions of a data packet, their transportblock size needs to be constant throughout the transmission of the datapacket (i.e., for the initial transmission and all retransmissions). Ifa change in the transport block size is signalled for a retransmission(i.e., the resource allocation in terms of the number of resource blocksallocated for the transmission and the modulation and coding schemeindex is resulting in another transport block size), the user equipmentcould interpret this combination of the New Data Indicator value being 1and the changing transport block size to instruct a deactivation of thesemi-persistent resource allocation.

The two alternative implementations described above may however have onedrawback: The resource release command is not allocating any resourcesto the user equipment so that it can only be used to release the grantfor the semi-persistent resource allocation. An alternative solution andaspect of the invention which would overcome such potential drawback isto adapt the RRC signaling procedure for configuring the semi-persistentresource allocation. In this alternative solution, the RRC signaling isindicating a special transport block size to the user equipment that,when indicated in a resource assignment for the semi-persistent resourceallocation is commanding the user equipment to deactivate thesemi-persistent resource allocation.

Hence, when signaling a resource assignment indicating this specificallydesignated transport block size (i.e., the number of resource blocksallocated for the transmission according to the resource allocationfield of the resource assignment and the modulation and coding schemeindex thereof is resulting in the specially designated transport blocksize), the user equipment may still use the resource assignment fortransmission/reception and will further deactivate the semi-persistentresource allocation for future transmissions/receptions. However, apotential drawback of this solution in comparison to using a specialcombination of the New Data Indicator value and modulation and codingscheme index may be that this solution would require changes to the RRCcontrol signalling specification.

Nevertheless, both solutions discussed above do not impact the userequipment's operation concerning the handling of resource assignments(grants) and do therefore also not impact the interface between Physicallayer and MAC layer as presently defined by the 3GPP.

Next the different aspects of the invention will be outlined in furtherdetail below under reference to a LTE-based mobile communication systemusing semi-persistent scheduling as outlined in the Technical Backgroundsection. FIG. 6 shows an exemplary signaling procedure for activating anuplink semi-persistent resource allocation between a user equipment (UE)and an eNode B according to an exemplary embodiment of the invention. Asindicated above, semi-persistent scheduling is configured using RRCsignalling between a user equipment and an eNode B (not shown in FIG.6). More specifically, the configuration of the semi-persistent resourceallocation via RRC signalling configures the periodicity (SPS intervalin FIG. 6) of the semi-persistent resource allocation, i.e., theperiodic time instances the user equipment is to receive data on thephysical downlink shared channel (PDSCH) or transmit data on thephysical uplink shared channel (PUSCH). By convention, the transmissionoccurring to/from the user equipment at the indicated periodic timeinstances are initial transmissions of data. Retransmission forsemi-persistently scheduled initial transmissions are either indicatedby a PDCCH, i.e., explicitly scheduled or—for the uplink case—could bealso triggered by a NACK in order to request a non-adaptiveretransmission.

Furthermore it should be noted that a PDCCH scheduling a SPSretransmission, the CRC of the PDCCH is also masked with the SPS C-RNTI.The distinction between (re)activation of semi-persistent scheduling andSPS retransmissions is done based on the NDI. For example a NDI bitvalue set to 0 indicates an activation of semi-persistent allocation,whereas a NDI bit value set to 1 indicates a retransmission.

The actual activation of semi-persistent scheduling is realized bysending a PDCCH including a resource allocation to the user equipment inwhich the NDI value is set to 0 (SPS PDCCH). The NDI bit value set to 0in connection with the resource allocation related to semi-persistentscheduling activates (or reactivates, i.e., overwrites the grant of aprevious activation) the semi-persistent scheduling—given that a validtransport block size is signalled by the SPS PDCCH. The resourceallocation is protected by a CRC field masked with an RNTI specificallyassigned to the user equipment for control signalling procedures relatedto the semi-persistent scheduling of uplink or downlink resources, suchas the SPS C-RNTI of the user equipment. In case the CRC field of aPDCCH (respectively, the content of the PDCCH) is being masked with theSPS C-RNTI of the user equipment this means that the PDCCH controlinformation is for semi-persistent scheduling of this user equipment.

The PDCCH including the resource allocation is granting physical channelresources to the user equipment, same will periodically use fortransmissions/reception of data via PUSCH/PDSCH that is scheduled on asemi-persistent basis. Accordingly, the user equipment stores thecontent of the resource allocation on the PDCCH (and updates thereof).As mentioned above, the eNode B may or may not send a dynamic grant forretransmission of a semi-persistently scheduled initial transmission ofdata. If a dynamic grant for the SPS retransmission is sent 601, theuser equipment obeys same, otherwise, if no dynamic grant is sent 602the user equipment uses the already granted physical resources used forthe previous transmission of the packet for the retransmission, i.e.,non-adaptive retransmission.

FIG. 7 shows an exemplary signaling procedure for deactivating an uplinksemi-persistent resource allocation between a user equipment and aneNode B according to an exemplary embodiment of the invention. Forexemplary purposes it is assumed that a uplink semi-persistent resourceallocation has been configured before, for example as shown in FIG. 6.In this exemplary embodiment of the invention, it is assumed that theeNode B sends a PDCCH for the semi-persistent resource allocation of theuser equipment, here a SPS UL PDCCH (deactivation), that is containing aspecial combination of NDI bit value and the modulation and codingscheme index comprised therein—see FIG. 5. In this exemplary embodiment,in order to signal an explicit release of uplink SPS resources, theeNode B sends a PDCCH for semi-persistent scheduling (re)activation (SPSUL PDCCH (deactivation)) which does not provide any transport block sizeinformation. This will be interpreted by the user equipment as a commandto release the semi-persistent scheduling resources, i.e., to deactivatethe semi-persistent scheduling (e.g., until the next activation isreceived). Furthermore, it should be noted that the PDCCH fordeactivating the semi-persistent resource allocation can be sent at anytime instant, e.g., in response to the eNode B detecting a no-speechperiod in VoIP communication transmitted using semi-persistentscheduling.

In a more specific exemplary embodiment of the invention, it is assumedthat the modulation and coding scheme field (MCS index) is defined as in3GPP TS 36.213, section 8.61 (see Table 8.6.1-1) for the uplink, shownin Table 1 below:

TABLE 1 Modulation Order Error! Objects cannot be created fromRedundancy MCS Index editing field TBS Index Version I_(MCS) codes.I_(TBS) rν_(idx) 0 2 0 0 1 2 1 0 2 2 2 0 3 2 3 0 4 2 4 0 5 2 5 0 6 2 6 07 2 7 0 8 2 8 0 9 2 9 0 10 2 10 0 11 4 10 0 12 4 11 0 13 4 12 0 14 4 130 15 4 14 0 16 4 15 0 17 4 16 0 18 4 17 0 19 4 18 0 20 4 19 0 21 6 19 022 6 20 0 23 6 21 0 24 6 22 0 25 6 23 0 26 6 24 0 27 6 25 0 28 6 26 0 29reserved 1 30 2 31 3

For the uplink, a PDCCH indicating a modulation and coding scheme index(IMcs) between 29 and 31 is indicating no transport block sizeinformation (TBS Index) and is commonly not used for (re)activation ofsemi-persistent scheduling. According to this exemplary embodiment, forsignaling an explicit SPS resource release command, the eNode B signalsan uplink resource assignment the CRC of which is masked with SPS C-RNTI(SPS UL PDCCH) with the NDI bit set to 0, in order to indicateactivation of semi-persistent scheduling, and a modulation and codingscheme index equal to 29, 30 or 31. According to this embodiment, one(or more) of modulation and coding scheme indices 29 to 31 isinterpreted by the user equipment to deactivate the uplinksemi-persistent resource allocation (i.e., to release the currentlyvalid SPS grant) in case of an uplink PDCCH addressed with SPS C-RNTIand NDI bit set to 0 is received. This is exemplarily illustrated in themodified excerpt of Table 1 below:

TABLE 2 Modulation Order Error! Objects cannot be created Redundancy MCSIndex from editing field TBS Index Version I_(MCS) codes. I_(TBS)rν_(idx)  0 2  0 0 . . . . . . . . . . . . 26 6 24 0 27 6 25 0 28 6 26 029 UL PDCCH with SPS C-RNTI 1 and NDI = 0: UL SPS release UL PDCCH withC-RNTI: reserved 30 reserved 2 31 3

In case semi-persistent scheduling has not been activated before, theuser equipment ignores the received SPS UL PDCCH.

The user equipment can distinguish between an SPS deactivation for adownlink semi-persistent resource allocation and an uplinksemi-persistent resource allocation based on the DCI format of thePDCCH. For example, the DCI format 0 as specified in 3GPP TS 36.213 isused in order to signal an uplink SPS resource release, whereas DCIformat 1 or 1A as specified in 3GPP TS 36.213 is used for a downlink SPSresource release.

In this connection it should be also noted that the definition of themodulation and coding scheme field for downlink transmissions isslightly differing from the definition for the uplink as shown in Table1 above. For downlink transmissions, the indices of the modulation andcoding scheme field are defined as shown in section 7.1.7.1 of 3GPP TS36.213 (see Table 7.1.7.1-1) which is shown below:

TABLE 3 Modulation MCS Index Order TBS Index I_(MCS) Q_(m) I_(TBS) 0 2 01 2 1 2 2 2 3 2 3 4 2 4 5 2 5 6 2 6 7 2 7 8 2 8 9 2 9 10 4 9 11 4 10 124 11 13 4 12 14 4 13 15 4 14 16 4 15 17 6 15 18 6 16 19 6 17 20 6 18 216 19 22 6 20 23 6 21 24 6 22 25 6 23 26 6 24 27 6 25 28 6 26 29 2reserved 30 4 31 6

Similar to the example for UL PDCCHs, the user equipment is interpretingone (or more) of the modulation and coding scheme indices 29 to 31 as adeactivation command for the downlink semi-persistent resourceallocation (i.e., to release the currently valid SPS grant) in case of aDL PDCCH addressed with SPS C-RNTI and NDI bit set to 0 is received.Accordingly, in a further exemplary embodiment the definitions of Table3 above are redefined as follows:

TABLE 4 Modulation MCS Index Order TBS Index I_(MCS) Q_(m) I_(TBS)  0 2 0 . . . . . . . . . 26 6 24 27 6 25 28 6 26 29 2 DL PDCCH with SPSC-RNTI and NDI = 0: DL SPS release DL PDCCH with C-RNTI: reserved 30 4reserved 31 6

In a further embodiment of the invention, the three MCS indices 29, 30and 31 shown in Tables 1 and 3 above are reused to identify whether theuplink, downlink, or uplink and downlink resources of thesemi-persistent resource allocation should be released. Accordingly, onepossible definition of the meaning of the modulation and coding schemeindices 29 to 31 in an uplink and/or downlink SPS PDCCH with the NDI bitset to 0 could be defined as follows:

TABLE 5 MCS Index I_(MCS) Command 29 PDCCH with SPS C-RNTI and NDI = 0:Release UL SPS only 30 PDCCH with SPS C-RNTI and NDI = 0: Release DL SPSonly 31 PDCCH with SPS C-RNTI and NDI = 0 Release UL & DL SPS

One benefit of this exemplary embodiment may be seen in that only oneDCI format of the PDCCH needs to be used for the SPS deactivationsignaling for the downlink as well as for the uplink direction, incomparison to the embodiments discussed with respect to Tables 1 to 4above, where the user equipment distinguished uplink and downlink SPSdeactivation based on the PDCCH's DCI format.

For example, the smallest DCI format, i.e., smallest PDCCH payload size,could be used for the SPS release indication, which would improve theradio efficiency. Alternatively the DCI format allowing the mostpossible “virtual CRC” bits can be used in order to reduce the falserelease probability.

Generally, since the CRC field of a PDCCH indicating a release of SPSresource is masked with the SPS C-RNTI of the addressed user equipmentand the NDI bit of the PDCCH is set to zero, a PDCCH indicating a SPSrelease can be seen as a special SPS activation PDCCH. As alreadymentioned, the activation of SPS is indicated by a PDCCH addressed tothe UE's SPS C-RNTI with the NDI bit set to zero. Basically, an “SPSrelease” PDCCH can be understood as an “SPS activation” PDCCH with theMCS field set to some reserved predetermined MCS indice(s), e.g., MCSindices 29 to 31. Expressed in another way, a SPS release indication canbe seen as an SPS activation indication providing no Transport blocksize information.

Therefore, the embodiments of the invention may be advantageouslycombined with several techniques aiming at reducing the false SPSactivation rate that are currently under discussion within 3GPP for theSPS activation (see the Technical Background section above). One meansto lower the false alarm rate to an acceptable level is to extend to CRClength virtually by setting fixed and known values/indices to some ofthe PDCCH fields that are not useful for semi-persistent scheduling.

Generally, the virtual CRC extension that can be applied to an SPSactivation PDCCH is also applicable to the SPS resource release PDCCH soas to lower the false alarm rate of a UE falsely considering a PDCCH tobe destined to itself. In more detail, the length of the 16-bit CRCfield of the PDCCH indicating a release of SPS resources can bevirtually extended by setting fixed and known values to some of thePDCCH fields that are not useful for semi-persistent schedulingactivation respectively release. For instance, for a UL PDCCH indicatingthe release of DL SPS resource the TPC field can be set to “00” and/orthe cyclic shift DM RS field can be set to “000”, for a DL PDCCHindicating the release of DL SPS resources the HARQ process ID field canbe set to “000” and the RV field can be set to “00”. Similarly theResource allocation field within a PDCCH indicating a release of SPSresources can be set to a fixed predetermined value.

The UE can verify a received PDCCH with the CRC masked by theSemi-Persistent C-RNTI, and when the new data indicator field is set tozero, as a valid SPS release indication by checking that these fieldswhich are used for the virtual CRC extension are set to the correctvalues. Only if the UE verified the received downlink controlinformation on the PDCCH as a valid semi-persistent release indication,the UE releases the configured SPS resources. Thereby, the probabilityof a falsely received PDCCH indicating SPS release can be lowered in thesame way as for the SPS activation. Hence the average time of falsesemi-persistent scheduling releases can be significantly increased.

It should be noted that the term DL PDCCH is used here to indicate aPDCCH with a DCI format used for PDSCH scheduling like for example DCIformat 1 or 1A or 2. In the same way, the term UL PDCCH should beunderstood as a PDCCH with a DCI format used for scheduling PUSCH, likefor example DCI format 0.

Next, the operation of Physical Layer and MAC Layer upon reception of aSPS PDCCH according to different embodiments of the invention will bedescribed in further detail. Please note that in the following adistinction between an uplink SPS resource release and a downlink SPSresource release is made only where appropriate. Generally, theexplanations are equally applicable to the processing of SPS UL PDCCHand SPS DL PDCCH, unless indicated otherwise. Furthermore, thedescription of FIG. 9 and FIG. 10 below assume for exemplary purposesonly that the PDCCH comprises a resource assignment as shown in FIG. 5.

FIG. 9 shows an exemplary handling of a received PDCCH at the PhysicalLayer and the MAC Layer of a user equipment. In this context, it shouldbe noted that the flow chart of FIG. 9 is only illustrating the mostimportant steps in view of the concept of the invention. Obviously, aswill be partly explained in more detail below, further steps may beperformed as required to properly process a PDCCH at the user equipment.

The user equipment first receives 901 a PDCCH and checks 902 whether ornot the PDCCH is comprising a CRC field masked with an SPS C-RNTI of theuser equipment. If not, i.e., the PDCCH's CRC is masked with a C-RNTI,the user equipment processes 903 the PDCCH as a dynamic grant forscheduled transmissions/receptions. In case the PDCCH is addressed tothe user equipment with its SPS C-RNTI, the Physical layer entity of theuser equipment is checking 904 the NDI bit value. If the NDI bit valueis equal to 1, the SPS PDCCH is for a retransmission ofsemi-persistently scheduled data and is processed 905 accordingly.

If the NDI bit is equal to 0, i.e., the PDCCH is an SPS (re)activation,the Physical layer entity of the user equipment further processes otherPDCCH fields like the modulation and coding scheme field (MCS field).

In this exemplary embodiment, if a modulation and coding scheme index of29 or higher is signaled and the SPS PDCCH is for uplink semi-persistentscheduling, the redundancy version (RV) is for example set to 1 formodulation and coding scheme index 29 (see Tables 1 and 2 above) and thetransport block size is set to “undefined”, i.e., no indication oftransport block size.

Consequently the Physical layer entity of the user equipment reports 909a received UL PDCCH addressed to the SPS C-RNTI with NDI bit equals 0,RV=1 and transport block size=“undefined” to the MAC layer entity of theuser equipment. The MAC layer entity is generally responsible for thescheduling and thus also handles SPS related operations. In case thereception of an UL PDCCH addressed with SPS C-RNTI, NDI=0, RV=1 and TBsize=“undefined” is reported from the Physical layer entity, the MAClayer entity detects 910 the uplink SPS resource release based on themissing transport size information for an SPS activation PDCCH.Accordingly, the user equipment deletes the stored grant for thesemi-persistent resource allocation and stops transmitting (respectivelyreceiving) data according to the semi-persistent resource allocation.

In case the Physical layer entity is detecting a modulation and codingscheme index smaller than 29 being signaled in the SPS PDCCH, thePhysical layer determines the signaled transport block size from themodulation and coding scheme index and the number of allocated resourceblocks in the resource assignment (RA) field, and provides 907 anindication on the reception of an SPS PDCCH together with the determinedtransport block size, NDI=0, and the signaled redundancy version to theMAC layer entity of the user equipment, which stores the informationprovided by the Physical layer entity and (re)activates thesemi-persistent resource allocation.

The procedure for a downlink SPS resource release can be implemented ina similar manner. However in this case a SPS DL PDCCH with modulationand coding scheme index of 29 would indicate an explicit modulationorder (see Tables 3 and 4 above) instead of an RV like for the uplink.Also for the downlink case, the transport block size would be“undefined” for a modulation and coding scheme index of 29 or higher,which would be reported to MAC layer entity in a similar fashion asexplained above. The MAC layer entity detects an SPS resource releasefor a downlink semi-persistent resource allocation based on the missingtransport block size information delivered from Physical layer entityfor the received SPS DL PDCCH.

It should be noted that the exemplary embodiments discussed with respectto FIG. 9 above assume that a modulation and coding scheme index of 29being sent in a SPS UL/DL PDCCH with a NDI bit value set to 0 istriggering the deactivation of the semi-persistent resource allocation.It is to be noted that also the modulation and coding scheme index of 30or 31 could be used instead, or as shown in Table 5, each of the withmodulation and coding scheme indices 29, 30 and 31 could trigger arespective deactivation of an uplink, downlink or uplink and downlinksemi-persistent resource allocation.

Another alternative exemplary handling of a received PDCCH at thePhysical Layer and the MAC Layer of a user equipment is shown in theflow chart of FIG. 10. In the embodiments discussed so far SPS releasesignaling has assumed that a SPS activation PDCCH is used where the NDIbit value is set 0. In this exemplary embodiment a PDCCH assigning a SPSretransmission, i.e., the NDI bit value is set to 1, indicates anexplicit release of SPS resources. For retransmissions the transportblock size needs to be constant for the all transmissions of a datapacket, i.e., its initial transmission and all retransmissions, if aHARQ protocol using soft combining is used—otherwise no soft combiningwould be possible. The case where the transport block size signaledwithin a PDCCH for a SPS retransmission differs from the transport blocksize used for the initial transmission could be interpreted as an SPSresource release. In the dynamic scheduling case the scenario wheretransport block size of retransmission is different from the initialtransport block size, is typically a HARQ protocol error. However forthe semi-persistent scheduling case this could be also used as a SPSresource release trigger.

Also with respect to FIG. 10, it should be noted that the flow chart isillustrating only the most relevant steps of this exemplary method.Obviously, as will be partly explained in more detail below, furthersteps may be performed as required to properly process a PDCCH at theuser equipment.

Similar to FIG. 9, the user equipment first receives 1001 a PDCCH andsubsequently checks 1002 whether or not the PDCCH is related tosemi-persistent scheduling by checking whether the CRC field has beenmasked with an SPS C-RNTI of the user equipment. If the PDCCH's CRC isnot masked with a user equipment's SPS C-RNTI, the user equipmentprocesses 1003 the PDCCH as a dynamic grant for scheduledtransmissions/receptions.

In case the PDCCH is addressed to the user equipment by means of usingan SPS C-RNTI, the Physical layer entity of the user equipment ischecking 1004 the NDI bit value. If the NDI bit is equal to 0, the SPSPDCCH is handled 1005 as a SPS activation or reactivation as in thestate of the art.

If the NDI bit value is 1, i.e., indicating the PDCCH being related to aretransmission for a semi-persistent resource allocation, the Physicallayer entity of the user equipment calculates 1006 the transport blocksize signaled in the PDCCH from the modulation and coding scheme indexand the number of allocated resource blocks comprised in the resourceassignment (RA) field of the PDCCH. Further, the Physical layer entityreports 1007 the calculated transport block size (TB S), the NDI and theredundancy version (RV) indicated in the PDCCH to the MAC layer entity.

The user equipment's MAC layer entity recognizes the PDCCH informationto indicate a retransmission of semi-persistently scheduled data andchecks 1008 whether or not the transport block size signaled in thePDCCH has changed in comparison to the transport block size signaled forthe initial semi-persistently scheduled transmissions. If the transportblock size is unchanged the user equipment is transmitting/receiving1009 the retransmission according to the grant of the PDCCH. If thetransport block size signaled in the PDCCH received in step 1001 haschanged, the MAC layer entity is interpreting 1010 the PDCCH as a SPSresource release. Accordingly, the MAC layer entity releases the relatedSPS grant for the semi-persistent resource allocation and isdeactivating the transmission of semi-persistently scheduled data.

Generally, it should be noted that upon uplink SPS deactivation, theuser equipment is not transmitting any data (This is commonly referredto a user equipment making a Discontinued Transmission (DTX)). Uponreceiving a downlink SPS deactivation, there are several alternativeshow the user equipment could react. For example, the user equipmentcould not decode the PDSCH in response to a received PDCCH indicating aDL SPS resource release (downlink data is sent on the PDSCH within thesame TTI as the corresponding PDCCH) and would consequently transmit noACK or NACK in the uplink, i.e., DTX of HARQ feedback, or couldalternatively acknowledge the reception of the PDCCH by sending anacknowledgement (ACK) for the PDCCH to the eNode B.

In particular, in prior art systems like the current specified LTE-basedmobile communication system the transmission of HARQ ACKs and NACKs onthe uplink is only foreseen for transport blocks of the shared channelPDSCH corresponding to the PDCCH. The POOCH itself cannot beacknowledged with an ACK or NACK message. Therefore, the DL SPS releasemessage encoded into the DL PDCCH cannot be acknowledged in the priorart. It should be noted that the term DL PDCCH is used here, to indicatea PDCCH with a DCI format used for PDSCH scheduling like for example DCIformat 1 or 1A or 2. In the same way, the term UL PDCCH should beunderstood as a PDCCH with a DCI format used for scheduling PUSCH, likefor example DCI format 0.

However, according to an embodiment of the invention, a DL PDCCHindicating a release of DL SPS resources is acknowledged by the UE bymeans of sending an HARQ ACK in response thereto to the eNode B (eNB).The possibility of acknowledging a DL PDCCH increases the reliability ofthe SPS release mechanism, since it is possible for the eNB to determinewhether the UE has correctly received the SPS release instruction. Incase that the eNB detects no HARQ ACK in response to having sent a SPSrelease indication, the eNB could repeat the DL PDCCH indicating therelease of DL SPS resources.

As already mentioned, in prior art systems the HARQ receiver whichresides in the UE for the downlink direction acknowledges or does notacknowledge the correct reception, respectively correct decoding, of atransport block received on the DL-SCH by sending an HARQ ACK/NACK tothe HARQ transmitting entity for the uplink direction which resides inthe eNB. The HARQ ACK/NACK is for example transmitted on an uplinkphysical control channel (PUCCH) or could be also multiplexed withhigher layer data on the UL shared channel (UL-SCH).

Further details on the determination of the uplink resource for HARQACK/NACK can be found in section 10.1 of 3GPP TS36.213 version 8.4.0.

The uplink resources for the HARQ ACK/NACK transmission are generallyimplicitly assigned by the DL PDCCH indicating the correspondingscheduled downlink shared channel transmission. As already outlined,when receiving a DL PDCCH indicating the release of DL SPS resourcesthere is no corresponding DL-SCH transmission, i.e., no transport blockis transmitted together with a DL PDCCH indicating a release of DL SPSresources. The DL PDCCH is only commanding the release of thesemi-persistent scheduling resources but does not grant a physicalchannel resource for receiving a transport block on the DL-SCH.Nonetheless, the UE could use the uplink resources assigned for the HARQACK/NACK for a received transport block on the DL-SCH in order toconfirm/acknowledge the reception of a DL PDCCH indicating a release bymeans of an HARQ ACK. Also the timing of the HARQ ACK confirming thereception of the DL PDCCH indicating a release of SPS resources could bethe same as for a received transport block on DL-SCH.

The above embodiment applies for the downlink SPS release via the DLPDCCH. For the uplink, in case the UL SPS release is transmitted via aUL PDCCH, it is not possible to confirm the reception of the UL PDCCHindicating a release of uplink SPS resources by an HARQ ACK in the sameway as for the downlink case in order to achieve the same reliabilityfor the SPS release procedure. More specifically, for the case of ULassignments there are no resources available for an HARQ ACK/NACK sentby the UE on the uplink, since for the uplink direction the HARQACK/NACK is sent by the eNB in the downlink. In detail, when the UEreceives an UL assignment indicated by a PDCCH, a transport block istransmitted in response thereto on the UL-SCH to the corresponding eNB,that in turn acknowledges the reception/decoding of the transport blockfrom the UE by an HARQ ACK/NACK. Thus, the acknowledgment of the ULPDCCH would require a completely new and complex UE behavior, whichwould hinder the acknowledgment of any UL SPS release mechanism.

Another embodiment of the invention allows the use of a DL PDCCH forreleasing also UL SPS resources, thus enabling the acknowledgment of thereception of the PDCCH indicating a release of UL SPS resources byacknowledging the DL PDCCH. In more detail, the embodiment explainedwith reference to Table 5 introduced the possibility to use the multipleMCS indices, e.g., 29, 30 and 31 in order to identify whether theuplink, downlink or uplink and downlink SPS resources should bereleased. One benefit is that only one DCI format for the PDCCH needs tobe used to indicate the release of SPS resources for downlink as well asfor uplink direction, compared to other embodiments (referring todescription for Tables 1 to 4), where the UE distinguishes uplink anddownlink SPS deactivation/release based on the PDCCH's DCI format.

In one exemplary embodiment the release of DL SPS resources is indicatedby a PDCCH scheduling a PDSCH transmission having the CRC masked withthe SPS C-RNTI, the NDI bit set to zero and the modulation and codingscheme index equal to 31 or respectively ‘11111’ in binary notation. Therelease of uplink SPS resources is similarly indicated by a PDCCHscheduling a PDSCH transmission having the CRC masked with the SPSC-RNTI, the NDI bit set to zero and the modulation and coding schemeindex equal to 30 or respectively ‘11110’ in binary notation.

Consequently, the DCI format could be for example 1, 1A or 2 when usingthe DL PDCCH for releasing the DL SPS resources. In addition, when usingDCI format 1 or 1A, the DL PDCCH may further contain another MCS Indexfor indicating the UL SPS resource release, e.g., MCS Index 29 in Table5. As a result, the UL SPS resource release indication can also beacknowledged by the UE through an HARQ ACK sent in response to thereceived DL PDCCH indicating release of UL SPS resources, and thus thesame high reliability can be achieved for UL as for DL SPS deactivation.

Using the DCI format 1A in order to indicate UL as well as DL SPSresource release would have the advantages, that a DCI format 1A can bedecoded by each UE which is configured by higher layers to decode PDCCHswith the CRC masked by the SPS C-RNTI. Furthermore, the DCI format 1A ismonitored by the mobile in the common search space as well as in theUE-specific search irrespective of the downlink transmission mode.Another advantage would be that the DCI format 1A denotes the DCI formatwith the smallest payload which is used for semi-persistent schedulingrelated control signalling. Details on the UE procedure related tomonitoring of PDCCH for control information can be found in section9.1.1 of TS36.213 version 8.4.0.

One potential advantage of the embodiments discussed above, inparticular with respect to FIGS. 7, 9 and 10, is that no changes toexisting PDCCH fields as specified for LTE are required and further, noadaption of the Physical layer-to-MAC layer interface in the userequipments is required. Another potential advantage is that no changesto the grant reception procedure in the user equipment are necessary.The Physical layer entity of the user equipment can receive an UL/DLPDCCH and reports the received resource assignment on the PDCCH togetherwith the corresponding HARQ information to the MAC layer entity. Theuser equipment's MAC layer entity can perform the necessary operationsfor dynamically scheduled respectively semi-persistently scheduledtransmissions, i.e., HARQ operations, based on the received informationfrom the Physical layer entity.

In contrast, the solution discussed in the Technical Background sectionof introducing a SPS resource allocation size of zero (“ORBs”) todeactivate a semi-persistent resource allocation would for examplerequire that the Physical layer entity detects an SPS resource releasebased on the “ORBs” indication within the resource allocation field andreports this to MAC layer entity. This in turn requires a newinter-layer signaling between Physical layer entity and MAC layer entityin the user equipment, since in the current LTE standards, the MAC layerentity performs the scheduling operation, i.e., detecting of SPSactivation/retransmission/resource release and performing thecorresponding actions, as described above.

In the embodiments discussed above with respect to FIGS. 7, 9 and 10, ithas been assumed that the modulation and coding scheme index that—incombination with the value of the NDI—is indicating the deactivation ofthe semi-persistent resource allocation is an index that is indicatingno transport block size, i.e., which is not suitable for the activationor reactivation of semi-persistent scheduling. However it should benoted that it is not necessarily required to use only one of themodulation and coding scheme indices for deactivating thesemi-persistent scheduling, that does not provide a transport block sizeinformation, such as indices 29, 30 and 31 shown in Tables 1 to 5 above.It is generally possible to reserve any arbitrary modulation and codingscheme index out of the modulation and coding scheme indicesrepresentable according to the given modulation and coding scheme fieldsize (e.g., 5 bits resulting in 32 indices), in order to indicate a SPSresource release. Obviously the selected modulation and coding schemeindex may thus not be used for an SPS activation or reactivation.

The selection of a modulation and coding scheme index indicating a validtransport block size may be nevertheless advantageous in connection withtrying to reduce the probability of a false SPS activation by settingfixed and known values to some of the PDCCH fields. According to oneexemplary embodiment of the invention only a limited number ofmodulation and coding scheme indices out of the set of available indicescould be allowed for use in a PDCCH that is activating or reactivatingsemi-persistent scheduling. For example, those “allowed indices” mightbe those modulation and coding scheme indices the most significant bitof which is 0, so that allowed range of modulation and coding schemeindices that can be used to activate or reactivate a semi-persistentresource allocation is restricted to indices 0 to 15 when exemplarilyconsidering a 5 bit modulation and coding scheme field as exemplified inTables 1 to 4 above. Any PDCCH that is indicating SPS (re)activation(CRC is masked with SPS C-RNTI and the NDI bit value is set to 0) andfurther indicating a modulation and coding scheme index outside theallowed range—i.e., the indicated modulation and coding scheme index inthe PDCCH is >15—would be ignored by the user equipment's Physical layerentity, i.e., the PDCCH is not reported to the MAC layer entity and isthus not activating semi-persistent scheduling. According to thisembodiment, one of the 16 modulation and coding scheme indices allowedfor the activation of semi-persistent scheduling would thus have to beselected to indicate a deactivation of the semi-persistent scheduling.For example it could be defined that the highest modulation and codingscheme index within the allowed range of modulation and coding schemeindices used for a SPS (re)activation, indicates an SPS resourcerelease, e.g., modulation and coding scheme index 15. This would howeverreduce the number of modulation and coding scheme indices which could beeffectively used for an SPS (re)activation.

Another option may be to allow only a subset of possible modulation andcoding scheme indices for the activation or reactivation ofsemi-persistent scheduling as discussed above, but to use one or allother modulation and coding scheme indices invalid for the activation ofthe semi-persistent scheduling as an explicit SPS resource releaseindication. For example, if modulation and coding scheme indices 0 to 15are defined allowable for activating semi-persistent scheduling, themodulation and coding scheme index of 16 could be used to command to theuser equipment to release to corresponding SPS resource. When comparingthis option to the solution of defining one of the modulation and codingscheme indices valid for SPS activation as a SPS resource releaseindication, the advantage of this option is that the eNode B has morefreedom in choosing among indices can be used for SPS activation.

However, this embodiment and option may require a change to the Physicallayer operation of the user equipment and may also require furtherinter-layer communication between the Physical layer entity and the MAClayer entity in the user equipment depending on the implementation. Asthe MAC layer entity is only informed on the transport block sizesignaled in the PDCCH, the MAC layer entity is not informed and may notconclude on the actually signaled modulation and coding scheme index, asdifferent modulation and coding scheme indices may result in the sametransport block size depending on the number of resource blocks assignedto the user equipment. Hence, the processing of the PDCCH in thePhysical layer entity needs to be adapted to detect that the PDCCH issignaling a SPS deactivation by checking the NDI bit value and themodulation and coding scheme index in the SPS PDCCH.

Accordingly, the Physical layer entity could inform the MAC layer entityon a SPS resource release by indicating an “undefined” transport blocksize to the MAC layer entity in response to the NDI bit value in thePDCCH being set to 0 and a modulation and coding scheme field includes a(predetermined) index which is for example an invalid modulation andcoding scheme index for SPS activation. This possibility would requireonly a change to the processing of the PDCCH in the Physical layerentity, however no new inter-layer communication between Physical layerand MAC layer is needed. Alternatively, the Physical layer entity couldexplicitly inform the MAC layer entity on a SPS resource release byintroducing a respective inter-layer communication between Physicallayer entity and MAC layer entity in the user equipment.

Next, further embodiments of the invention according to the secondaspect of the invention will be discussed with respect to FIGS. 8, 11,12 and 13. In contrast to using a predetermined combination (orcombinations) of the NDI bit value and modulation and coding schemeindex (indices) to signal a SPS resource release, the followingembodiments discussed with respect to FIGS. 8, 11, 12 and 13 use aspecially designated transport block size that is indicating an SPSresource release to the user equipment. The embodiments according tothis alternative aspect of the invention may be advantageously combinedwith several techniques aiming at reducing the false SPS activation ratethat are currently under discussion within 3GPP (see the TechnicalBackground section above). One means to lower the false alarm rate to anacceptable level is to extend to CRC length virtually by setting fixedand known values/indices to some of the PDCCH fields that are not usefulfor semi-persistent scheduling. Further, another possibility used in oneembodiment of the invention is to restrict the set of transport blocksizes, which is allowed for an SPS activation.

In the current LTE specification, semi-persistent scheduling isconfigured by RRC signaling using a message, which includessemi-persistent scheduling related parameters. This message includes theSPS periodicity (SPS Interval in FIG. 6) and—for downlinksemi-persistent scheduling operation—HARQ process information.

According to this exemplary embodiment, the RRC signaling message forconfiguring the semi-persistent scheduling further includes informationon allowed transport block sizes, i.e., transport block sizes that maybe used in connection with an SPS activation or reactivation. Every timea PDCCH for SPS activation is received at the MAC layer entity, the MAClayer entity checks whether the indicated transport block size in thePDCCH is within the set of allowed transport block sizes, i.e., is avalid transport block size for SPS activation. Since the transport blocksize signaled in a PDCCH depends on the number of allocated resourceblocks and the modulation and coding scheme, one alternative would be tosignal a minimum and maximum allowed transport block size within the SPSconfiguration message to indicate a range of transport block sizes thatcan be used for SPS activation or reactivation. All transport blocksizes between this minimum and maximum value would thus be validtransport block sizes for an SPS activation or reactivation. It shouldbe noted that there are also further alternative how to restrict theallowed transport block sizes for a semi-persistent scheduling(re)activation, for example by signaling via RRC the correspondingmodulation and/or coding scheme indices and resource allocation sizesresulting in valid transport sizes.

For the indication of an SPS resource release, the RRC protocol could befurther modified to include to the SPS configuration related parametersa predetermined transport block size, which when signaled in a PDCCH isindicating a SPS resource release. This transport block size is referredto as “release TBS” in the following. FIG. 12 exemplarily illustrates aSPS configuration message according to an exemplary embodiment of theinvention including a “release TBS” field that is indicating thespecified release TBS value.

FIG. 8 shows an exemplary signaling procedure for deactivating an uplinksemi-persistent resource allocation between a user equipment and aneNode B according to an exemplary embodiment of the invention, where aRRC configured release TBS is used to deactivate a semi-persistentresource allocation to the user equipment. In comparison to thesignaling in FIG. 7, it should be noted that the deactivation ofsemi-persistent scheduling according to the exemplary embodiment in FIG.8 has the advantage that the PDCCH is not only commanding thedeactivation of the semi-persistent scheduling but also grants aphysical channel resource for receiving/transmitting a final datapacket.

The signaling in FIG. 8 is essentially similar to that shown in FIG. 7.However, the SPS UL PDCCH for deactivating the semi-persistent resourceallocation (SPS UL PDCCH (deactivation)) is yielding the release TBS bysignaling a corresponding number of allocated resource blocks andmodulation and coding scheme index resulting in this transport blocksize. As indicated above, a further difference to the signaling in FIG.7 is that the SPS UL PDCCH (deactivation) is not only triggering thedeactivation of the semi-persistent resource allocation at the userequipment but is so-to-say also providing at the same time a dynamicgrant for one further transmission using the resource allocation andtransport format signaled within the SPS UL PDCCH (deactivation) i.e.,in this example the uplink semi-persistent scheduling is deactivatedupon having received the SPS UL PDCCH (deactivation) and the UE ismaking one initial data uplink transmission according to the uplinkassignment signaled within the SPS UL PDCCH (deactivation) (initialtransmission with dynamic grant from SPS UL PDCCH (deactivation)) andcorresponding retransmissions, if any).

Although the example in FIG. 8 is related to uplink semi-persistentscheduling, it should be noted that this concept may be equally appliedto downlink semi-persistent scheduling. In the latter case the SPS DLPDCCH (deactivation) will indicate a downlink transmission on theresources and with the transport format as indicated in the SPS DL PDCCH(deactivation) and furthermore the deactivation of the downlinksemi-persistent scheduling at the user equipment. For example the eNodeB could signal a release of semi-persistent scheduling and, at the sametime, a RRC message for releasing the bearer using the semi-persistentlyscheduled resources, i.e., a VoIP bearer.

FIG. 11 is showing a flow chart of the operation of Physical layerentity, MAC layer entity and RRC entity within a user equipmentaccording to another embodiment of the invention in case a release TBSis used to indicate a SPS resource release to the user equipment. FIG.11 is not distinguishing between uplink semi-persistent scheduling anddownlink semi-persistent scheduling but the basic steps shown in theflow chart equally apply to both scenarios.

As indicated above, semi-persistent scheduling of the user equipment isconfigured 1101 by means of a corresponding RRC configuration message asfor example exemplarily depicted in FIG. 12 or FIG. 13 that is sent bythe serving eNode B. The RRC entity of the user equipment is thus awareof the release TBS (TB S.sub.release) upon having received suchconfiguration message. The RRC entity provides 1102 the release TBS tothe MAC layer entity, which is storing 1103 the release TBS.

Upon reception 1104 of a PDCCH at the Physical layer entity of the userequipment, the Physical layer entity is checking 1105, whether the CRCfield of the PDCCH has been masked by the eNode B with a SPS C-RNTI ofthe user equipment, i.e., whether it is destined to the user equipmentand whether it is related to semi-persistent scheduling. In case thePDCCH's CRC field is not masked with the SPS C-RNTI of the userequipment, the Physical layer entity processes 1106 the PDCCH as adynamic grant. Otherwise, the Physical layer entity is checking 1107next, whether the NDI bit value is set to 0 thereby detecting whetherthe SPS PDCCH is relating to an activation respectively deactivation ofthe semi-persistent scheduling or a retransmission of asemi-persistently scheduled initial transmission. In case the SPS PDCCHis for a retransmission of a semi-persistently scheduled initialtransmission, the SPS PDCCH is further processed 1108 accordingly.

If the SPS PDCCH indicates an activation respectively deactivation ofthe semi-persistent scheduling, the Physical layer entity is calculating1109 the transport block size (TBS) signaled in the SPS PDCCH and isreporting 1110 the transport block size, the NDI and the redundancyversion (RV) signaled in the SPS PDCCH to the MAC layer entity. The MAClayer entity checks 1111, whether the SPS PDCCH indicates a transportblock size (TBS) that is equal to the release TBS (TBS.sub.release) inorder to conclude, whether the SPS PDCCH is signaling an activation or adeactivation of the semi-persistent scheduling.

In case the MAC layer entity of the user equipment determines thetransport block size (TBS) signaled within the SPS PDCCH equals therelease TBS, the MAC layer entity of the UE will release 1113 thecorresponding SPS resource and will deactivate the semi-persistentscheduling. Furthermore, the user equipment processes the received SPSPDCCH in a similar fashion as a dynamic assignment andtransmits/receives a data packet accordingly. Otherwise, the MAC layerentity is concluding that the SPS PDCCH is signaling an activation ofthe semi-persistent scheduling. Accordingly, the MAC layer entity willstore/update 1112 the grant of the SPS PDCCH and (re)activate thesemi-persistent resource allocation.

The “release TBS” could be a transport block size outside the range ofvalid transport block sizes for SPS activation (outside the rangedefined by min TBS and max TBS) or could alternatively be a transportblock size within the signaled transport block size range allowed forSPS activation.

The release TBS approach described above in connection with FIGS. 8, 11and 12 has one potential advantage over the above described solutionswhere a combination of NDI bit value and modulation and coding schemeindex has been used to signal a SPS resource release. With the lattersolution an entire PDCCH is required in order to release SPS resources.There is no PDSCH respectively PUSCH allocation possible with this typeof release PDCCH, i.e., a release PDCCH that is signaling apredetermined combination of NDI bit value and modulation and codingscheme index cannot be used in order to allocate resource for an uplinktransmission or downlink reception, since no transport block sizeinformation can be provided by the PDCCH given that a modulation andcoding scheme index yielding no transport block size information is usedin the combination of NDI bit value and modulation and coding schemeindex indicating the SPS resource release.

In contrast thereto when defining a release TBS as described above, itis possible to allocate PDSCH respectively PUSCH with the release PDCCH.As described above in connection with FIG. 8, the user equipment whenreceiving a SPS PDCCH indicating the release TBS UE will release thecorresponding SPS resources and obey the assignment signaled by the SPSPDCCH as in case a normal dynamic grant has been received. It should benoted that even though the PDCCH is addressed with the SPS C-RNTI, theuser equipment acts as having received a dynamic resource assignment inparallel to the SPS resource release indication. With respect to thePDCCH resource usage the definition of a release TBS may be thus moreefficient compared to the definition of a “release combination” of NDIbit value and modulation and coding scheme index.

On the other hand, the definition of a release TB S will introducechanges to the RRC message configuring the semi-persistent scheduling asthe user equipment needs to be informed on the release TBS. To avoid theoverhead of the signaling overhead for configuring the release TBS viathe RRC message, the release TBS could be a predefined value.Considering the exemplary RRC message format of FIG. 12, one optioncould be that the “release TBS” field is removed and the release TBS fordeactivating semi-persistent scheduling is implicitly given, i.e., the“min TBS” field or the “max TBS” field do not only indicate the validrange of transport block size that is allowed for SPS (re)activation butone of the two transport block sizes could also indicate the releaseTBS.

Alternatively, considering that the available resource allocation sizesin terms of resource blocks and available modulation and coding schemesfor semi-persistent scheduling yield a minimum or maximum transportblock size that can be signaled in a PDCCH, the smallest possibletransport block size or the highest possible transport block size thatcan be signaled in the PDCCH could implicitly indicate, i.e., define therelease TBS. In this alternative, the transport block size indicatingthe SPS resource release does not necessarily lie within the range ofthe valid transport block sizes for an SPS activation.

Furthermore, similar to the example discussed with Table 5 above, alsowhen defining a release TBS for semi-persistent scheduling, individualrelease TBSs for uplink, downlink and uplink and downlinksemi-persistent scheduling could be defined. This is exemplarily shownin FIG. 13, where the fields UL release TBS, DL release TBS and UL andDL release TB S individually indicate the transport block sizeindicating a release of uplink, downlink and uplink and downlink SPSresources, respectively. In this example, it is optionally furtherpossible to define that the SPS resources are only released in case sameare indicated in an SPS DL PDCCH or SPS UL PDCCH.

As a further variant of the second aspect of the invention where arelease TBS is used for indicated deactivation of semi-persistentscheduling, the RRC entity of the eNode B could also signal onecombination of modulation and coding scheme index and resourceallocation size instead of signaling a release TBS. The difference isthat there are potentially multiple combinations of modulation andcoding scheme indices and resource allocation size values whichcorrespond to the same TB size. In this case the Physical layer would berequired to check for an SPS resource release, i.e., check whether theRRC signaled combination of modulation and coding scheme index andresource allocation size was received by a SPS PDCCH and inform MAClayer correspondingly.

In the flow charts of FIGS. 9 to 11, it has been indicated that thePhysical layer entity first checks, whether the CRC field of the PDCCHis masked with the user equipment's SPS C-RNTI or not. Of course, thePhysical layer entity could also first check, whether the CRC field ofthe PDCCH is masked with the user equipment's C-RNTI or not to determinewhether it is a dynamic grant and, if not, could subsequently checkwhether the CRC field of the PDCCH is masked with the user equipment'sSPS C-RNTI or not.

Another embodiment of the invention relates to the implementation of theabove described various embodiments using hardware and software. It isrecognized that the various embodiments of the invention may beimplemented or performed using computing devices (processors). Acomputing device or processor may for example be general purposeprocessors, digital signal processors (DSP), application specificintegrated circuits (ASIC), field programmable gate arrays (FPGA) orother programmable logic devices, etc. The various embodiments of theinvention may also be performed or embodied by a combination of thesedevices.

Further, the various embodiments of the invention may also beimplemented by means of software modules, which are executed by aprocessor or directly in hardware. Also a combination of softwaremodules and a hardware implementation may be possible. The softwaremodules may be stored on any kind of computer readable storage media,for example RAM, EPROM, EEPROM, flash memory, registers, hard disks,CD-ROM, DVD, etc.

Furthermore, it should be noted that the terms mobile terminal andmobile station are used as synonyms herein. A user equipment may beconsidered one example for a mobile station and refers to a mobileterminal for use in 3GPP-based networks, such as LTE.

In the previous paragraphs various embodiments of the invention andvariations thereof have been described. It would be appreciated by aperson skilled in the art that numerous variations and/or modificationsmay be made to the present invention as shown in the specificembodiments without departing from the spirit or scope of the inventionas broadly described.

It should be further noted that most of the embodiments have beenoutlined in relation to a 3GPP-based communication system and theterminology used in the previous sections mainly relates to the 3GPPterminology. However, the terminology and the description of the variousembodiments with respect to 3GPP-based architectures are not intended tolimit the principles and ideas of the inventions to such systems.

Also the detailed explanations given in the Technical Background sectionabove are intended to better understand the mostly 3GPP specificexemplary embodiments described herein and should not be understood aslimiting the invention to the described specific implementations ofprocesses and functions in the mobile communication network.Nevertheless, the improvements proposed herein may be readily applied inthe architectures described in the Technical Background section.Furthermore, the concept of the invention may be also readily used inthe LTE RAN currently discussed by the 3GPP.

The invention claimed is:
 1. A method for releasing a semi-persistentscheduled (SPS) resource allocation in a mobile communication system,wherein a user equipment performs the steps of: receiving controlsignaling via a physical downlink control channel (PDCCH), and releasingthe semi-persistent scheduled resource allocation when a set ofconditions is met including when a modulation coding scheme index in thereceived control signaling includes an index in a predetermined subsetof the set of modulation coding scheme indices, wherein thepredetermined subset of the set of modulation coding scheme indices haveindices with undefined or reserved representations of transport blocksize.
 2. The method according to claim 1, wherein the predeterminedsubset of the set of modulation coding scheme indices is a range ofmodulation coding scheme indices greater than a predetermined modulationcoding scheme index.
 3. The method according to claim 1, wherein eachmodulation coding scheme index in the set of modulation coding schemeindices includes an indicator of a modulation order value, an indicatorof a transport block size index, and an indicator of a redundancyversion.
 4. The method according to claim 1, wherein the predeterminedsubset of the set of modulation coding scheme indices includes amodulation and coding scheme index indicating no transport block sizeinformation.
 5. The method according to claim 1, wherein the set ofconditions includes a New Data Indicator value of
 0. 6. The methodaccording to claim 1, wherein the control signaling conveys controlinformation for scheduling of a Physical Uplink Shared Channel (PUSCH),and wherein the set of conditions further includes a transmit powercontrol (TPC) field being a defined TPC value.
 7. The method accordingto claim 6, wherein the defined TPC value is ‘00’.
 8. The methodaccording to claim 1, wherein the control signaling conveys controlinformation for scheduling of a Physical Downlink Shared Channel(PDSCH), and wherein the set of conditions further includes a RedundancyVersion (RV) field being a defined RV value.
 9. The method according toclaim 8, wherein the defined RV value is ‘00’.
 10. The method accordingto claim 1, further comprising: transmitting an acknowledgment messagethat acknowledges release of the semi-persistent scheduled resourceallocation.
 11. A user equipment for a mobile communication system,comprising: a receiver configured to receive control signaling via aphysical downlink control channel (PDCCH), and processing circuitryconfigured to release a semi-persistent scheduled (SPS) resourceallocation when a set of conditions is met including when a modulationcoding scheme index in the received control signaling includes an indexin a predetermined subset of the set of modulation coding schemeindices, wherein the predetermined subset of the set of modulationcoding scheme indices have indices with undefined or reservedrepresentations of transport block size.
 12. The user equipmentaccording to claim 11, wherein the predetermined subset of the set ofmodulation coding scheme indices is a range of modulation coding schemeindices greater than a predetermined modulation coding scheme index. 13.The user equipment according to claim 11, wherein each modulation codingscheme index in the set of modulation coding scheme indices includes anindicator of a modulation order value, an indicator of a transport blocksize index, and an indicator of a redundancy version.
 14. The userequipment according to claim 11, wherein the predetermined subset of theset of modulation coding scheme indices includes a modulation and codingscheme index indicating no transport block size information.
 15. Theuser equipment according to claim 11, wherein the set of conditionsincludes a New Data Indicator value of
 0. 16. The user equipmentaccording to claim 11, wherein the control signaling conveys controlinformation for scheduling of a Physical Uplink Shared Channel (PUSCH),and wherein the set of conditions further includes a transmit powercontrol (TPC) field being a defined TPC value.
 17. The user equipmentaccording to claim 16, wherein the defined TPC value is ‘00’.
 18. Theuser equipment according to claim 11, wherein the control signalingconveys control information for scheduling of a Physical Downlink SharedChannel (PDSCH), and wherein the set of conditions further includes aRedundancy Version (RV) field being a defined RV value.
 19. The userequipment according to claim 18, wherein the defined RV value is ‘00’.20. The user equipment according to claim 11, further comprising: atransmitter configured to transmit an acknowledgment message thatacknowledges release of the semi-persistent scheduled resourceallocation.